Slide 1
Slide 1 text
Jan 2015
@sandimetz
Sandi Metz
Nothing
is
Something
Slide 2
Slide 2 text
Jan 2015
@sandimetz
Slide 3
Slide 3 text
Jan 2015
@sandimetz
Slide 4
Slide 4 text
Jan 2015
@sandimetz
Smalltalk Infected
Slide 5
Slide 5 text
Jan 2015
@sandimetz
1.to_s
Slide 6
Slide 6 text
Jan 2015
@sandimetz
1.to_s
=>
"1"
Slide 7
Slide 7 text
Jan 2015
@sandimetz
1.to_s
=>
"1"
1.send(:to_s)
Slide 8
Slide 8 text
Jan 2015
@sandimetz
1.to_s
=>
"1"
1.send(:to_s)
=>
"1"
Slide 9
Slide 9 text
Jan 2015
@sandimetz
1.to_s
=>
"1"
1.send(:to_s)
=>
"1"
Slide 10
Slide 10 text
Jan 2015
@sandimetz
1.to_s
=>
"1"
1.send(:to_s)
=>
"1"
1
+
1
Slide 11
Slide 11 text
Jan 2015
@sandimetz
1.to_s
=>
"1"
1.send(:to_s)
=>
"1"
1
+
1
=>
2
Slide 12
Slide 12 text
Jan 2015
@sandimetz
1.to_s
=>
"1"
1.send(:to_s)
=>
"1"
1
+
1
=>
2
1.send(:+,
1)
Slide 13
Slide 13 text
Jan 2015
@sandimetz
1.to_s
=>
"1"
1.send(:to_s)
=>
"1"
1
+
1
=>
2
1.send(:+,
1)
=>
2
Slide 14
Slide 14 text
Jan 2015
@sandimetz
1.to_s
=>
"1"
1.send(:to_s)
=>
"1"
1
+
1
=>
2
1.send(:+,
1)
=>
2
Slide 15
Slide 15 text
Jan 2015
@sandimetz
1.class
1.to_s
=>
"1"
1.send(:to_s)
=>
"1"
1
+
1
=>
2
1.send(:+,
1)
=>
2
Slide 16
Slide 16 text
Jan 2015
@sandimetz
1.class
=>
Fixnum
1.to_s
=>
"1"
1.send(:to_s)
=>
"1"
1
+
1
=>
2
1.send(:+,
1)
=>
2
Slide 17
Slide 17 text
Jan 2015
@sandimetz
Fixnum.instance_methods(false)
=>
[
:to_s,
:+,
:-‐,
:*,
:/,
:==,
:%,
:modulo,
#
etc
1.to_s
=>
"1"
1.send(:to_s)
=>
"1"
1
+
1
=>
2
1.send(:+,
1)
=>
2
Slide 18
Slide 18 text
Jan 2015
@sandimetz
Fixnum.instance_methods(false)
=>
[
:to_s,
:+,
:-‐,
:*,
:/,
:==,
:%,
:modulo,
#
etc
1.to_s
=>
"1"
1.send(:to_s)
=>
"1"
1
+
1
=>
2
1.send(:+,
1)
=>
2
Slide 19
Slide 19 text
Jan 2015
@sandimetz
Fixnum.instance_methods(false)
=>
[
:to_s,
:+,
:-‐,
:*,
:/,
:==,
:%,
:modulo,
#
etc
1.to_s
=>
"1"
1.send(:to_s)
=>
"1"
1
+
1
=>
2
1.send(:+,
1)
=>
2
Slide 20
Slide 20 text
Jan 2015
@sandimetz
Fixnum.instance_methods(false)
=>
[
:to_s,
:+,
:-‐,
:*,
:/,
:==,
:%,
:modulo,
#
etc
1.to_s
=>
"1"
1.send(:to_s)
=>
"1"
1
+
1
=>
2
1.send(:+,
1)
=>
2
Slide 21
Slide 21 text
Jan 2015
@sandimetz
1.to_s
=>
"1"
1.send(:to_s)
=>
"1"
1
+
1
=>
2
1.send(:+,
1)
=>
2
1
==
1
Slide 22
Slide 22 text
Jan 2015
@sandimetz
1.to_s
=>
"1"
1.send(:to_s)
=>
"1"
1
+
1
=>
2
1.send(:+,
1)
=>
2
1
==
1
=>
true
Slide 23
Slide 23 text
Jan 2015
@sandimetz
1.to_s
=>
"1"
1.send(:to_s)
=>
"1"
1
+
1
=>
2
1.send(:+,
1)
=>
2
1
==
1
=>
true
Slide 24
Slide 24 text
Jan 2015
@sandimetz
1.to_s
=>
"1"
1.send(:to_s)
=>
"1"
1
+
1
=>
2
1.send(:+,
1)
=>
2
1
==
1
=>
true
true.class
Slide 25
Slide 25 text
Jan 2015
@sandimetz
1.to_s
=>
"1"
1.send(:to_s)
=>
"1"
1
+
1
=>
2
1.send(:+,
1)
=>
2
1
==
1
=>
true
true.class
=>
TrueClass
Slide 26
Slide 26 text
Jan 2015
@sandimetz
1.to_s
=>
"1"
1.send(:to_s)
=>
"1"
1
+
1
=>
2
1.send(:+,
1)
=>
2
1
==
1
=>
true
true.class
=>
TrueClass
Slide 27
Slide 27 text
Jan 2015
@sandimetz
1.to_s
=>
"1"
1.send(:to_s)
=>
"1"
1
+
1
=>
2
1.send(:+,
1)
=>
2
1
==
1
=>
true
true.class
=>
TrueClass
TrueClass.instance_methods(false)
=>
[
:to_s,
:inspect,
:&,
:|,
:^,
:pretty_print_cycle,
:pretty_print]
Slide 28
Slide 28 text
Jan 2015
@sandimetz
1.to_s
=>
"1"
1.send(:to_s)
=>
"1"
1
+
1
=>
2
1.send(:+,
1)
=>
2
1
==
1
=>
true
true.class
=>
TrueClass
TrueClass.instance_methods(false)
=>
[
:to_s,
:inspect,
:&,
:|,
:^,
:pretty_print_cycle,
:pretty_print]
Slide 29
Slide 29 text
Jan 2015
@sandimetz
‘Special’ syntax for booleans
Slide 30
Slide 30 text
Jan 2015
@sandimetz
Smalltalk keywords
true,
false,
nil,
self,
super,
thisContext
Slide 31
Slide 31 text
Jan 2015
@sandimetz
Smalltalk keywords
true,
false,
nil,
self,
super,
thisContext
Ruby keywords
alias
and
BEGIN
begin
break
case
class
def
defined?
do
else
elsif
END
end
ensure
false
for
if
in
module
next
nil
not
or
redo
rescue
retry
return
self
super
then
true
undef
unless
until
when
while
yield
Slide 32
Slide 32 text
Jan 2015
@sandimetz
Smalltalk keywords
true,
false,
nil,
self,
super,
thisContext
Ruby keywords
alias
and
BEGIN
begin
break
case
class
def
defined?
do
else
elsif
END
end
ensure
false
for
if
in
module
next
nil
not
or
redo
rescue
retry
return
self
super
then
true
undef
unless
until
when
while
yield
Slide 33
Slide 33 text
Jan 2015
@sandimetz
if
(1
==
1)
'is
true'
else
'is
false'
end
Slide 34
Slide 34 text
Jan 2015
@sandimetz
if
(1
==
1)
'is
true'
else
'is
false'
end
true
Slide 35
Slide 35 text
Jan 2015
@sandimetz
if
(1
==
1)
'is
true'
else
'is
false'
end
=>
'is
true'
true
Slide 36
Slide 36 text
Jan 2015
@sandimetz
if
(1
==
1)
code
to
eval
when
‘true’
else
code
to
eval
when
‘false’
end
true
Slide 37
Slide 37 text
Jan 2015
@sandimetz
if
(
truthy
)
code
to
eval
when
‘truthy’
else
code
to
eval
when
‘falsey’
end
Slide 38
Slide 38 text
Jan 2015
@sandimetz
if
(some
object
whose
type
I
know)
code
to
do
some
stuff
else
code
to
do
some
other
stuff
end
Slide 39
Slide 39 text
Jan 2015
@sandimetz
I just want to
send a message
to an object
Slide 40
Slide 40 text
Jan 2015
@sandimetz
Slide 41
Slide 41 text
Jan 2015
@sandimetz
if
Slide 42
Slide 42 text
Jan 2015
@sandimetz
if
is an enabler
Slide 43
Slide 43 text
Jan 2015
@sandimetz
‘Message sending’ syntax
for
TrueClass / FalseClass
Slide 44
Slide 44 text
Jan 2015
@sandimetz
class
TrueClass
end
Slide 45
Slide 45 text
Jan 2015
@sandimetz
class
TrueClass
def
if_true
yield
end
end
Slide 46
Slide 46 text
Jan 2015
@sandimetz
class
TrueClass
def
if_true
yield
self
end
end
Slide 47
Slide 47 text
Jan 2015
@sandimetz
class
TrueClass
def
if_true
yield
self
end
def
if_false
self
end
end
Slide 48
Slide 48 text
Jan 2015
@sandimetz
class
TrueClass
def
if_true
yield
self
end
def
if_false
self
end
end
class
FalseClass
def
if_true
self
end
def
if_false
yield
self
end
end
Slide 49
Slide 49 text
Jan 2015
@sandimetz
class
TrueClass
def
if_true
yield
self
end
def
if_false
self
end
end
class
FalseClass
def
if_true
self
end
def
if_false
yield
self
end
end
Slide 50
Slide 50 text
Jan 2015
@sandimetz
class
TrueClass
def
if_true
yield
self
end
def
if_false
self
end
end
class
FalseClass
def
if_true
self
end
def
if_false
yield
self
end
end
Slide 51
Slide 51 text
Jan 2015
@sandimetz
class
TrueClass
def
if_true
yield
self
end
def
if_false
self
end
end
class
FalseClass
def
if_true
self
end
def
if_false
yield
self
end
end
Slide 52
Slide 52 text
Jan 2015
@sandimetz
class
TrueClass
def
if_true
yield
self
end
def
if_false
self
end
end
class
FalseClass
def
if_true
self
end
def
if_false
yield
self
end
end
Slide 53
Slide 53 text
Jan 2015
@sandimetz
class
TrueClass
def
if_true
yield
self
end
def
if_false
self
end
end
class
FalseClass
def
if_true
self
end
def
if_false
yield
self
end
end
Slide 54
Slide 54 text
Jan 2015
@sandimetz
class
TrueClass
def
if_true
yield
self
end
def
if_false
self
end
end
class
FalseClass
def
if_true
self
end
def
if_false
yield
self
end
end
Slide 55
Slide 55 text
Jan 2015
@sandimetz
(1
==
1).if_true
{puts
"evaluated
block"}
Slide 56
Slide 56 text
Jan 2015
@sandimetz
(1
==
1).if_true
{puts
"evaluated
block"}
Slide 57
Slide 57 text
Jan 2015
@sandimetz
(1
==
1).if_true
{puts
"evaluated
block"}
true
Slide 58
Slide 58 text
Jan 2015
@sandimetz
(1
==
1).if_true
{puts
"evaluated
block"} class
TrueClass
def
if_true
yield
self
end
#
…
end
true
Slide 59
Slide 59 text
Jan 2015
@sandimetz
(1
==
1).if_true
{puts
"evaluated
block"} class
TrueClass
def
if_true
yield
self
end
#
…
end
Slide 60
Slide 60 text
Jan 2015
@sandimetz
(1
==
1).if_true
{puts
"evaluated
block"} class
TrueClass
def
if_true
yield
self
end
#
…
end
Slide 61
Slide 61 text
Jan 2015
@sandimetz
(1
==
1).if_true
{puts
"evaluated
block"}
"evaluated
block"
class
TrueClass
def
if_true
yield
self
end
#
…
end
Slide 62
Slide 62 text
Jan 2015
@sandimetz
(1
==
1).if_true
{puts
"evaluated
block"}
"evaluated
block"
(1
==
1).if_false
{puts
"evaluated
block"}
class
TrueClass
def
if_true
yield
self
end
#
…
end
Slide 63
Slide 63 text
Jan 2015
@sandimetz
(1
==
1).if_true
{puts
"evaluated
block"}
"evaluated
block"
(1
==
1).if_false
{puts
"evaluated
block"}
class
TrueClass
def
if_true
yield
self
end
def
if_false
self
end
end
Slide 64
Slide 64 text
Jan 2015
@sandimetz
(1
==
1).if_true
{puts
"evaluated
block"}
"evaluated
block"
(1
==
1).if_false
{puts
"evaluated
block"}
#
block
is
ignored
class
TrueClass
def
if_true
yield
self
end
def
if_false
self
end
end
Slide 65
Slide 65 text
Jan 2015
@sandimetz
(1
==
1).if_true
{puts
"evaluated
block"}
"evaluated
block"
(1
==
1).if_false
{puts
"evaluated
block"}
#
block
is
ignored
(1
==
2).if_true
{puts
"evaluated
block"}
Slide 66
Slide 66 text
Jan 2015
@sandimetz
(1
==
1).if_true
{puts
"evaluated
block"}
"evaluated
block"
(1
==
1).if_false
{puts
"evaluated
block"}
#
block
is
ignored
(1
==
2).if_true
{puts
"evaluated
block"}
Slide 67
Slide 67 text
Jan 2015
@sandimetz
(1
==
1).if_true
{puts
"evaluated
block"}
"evaluated
block"
(1
==
1).if_false
{puts
"evaluated
block"}
#
block
is
ignored
(1
==
2).if_true
{puts
"evaluated
block"}
false
Slide 68
Slide 68 text
Jan 2015
@sandimetz
(1
==
1).if_true
{puts
"evaluated
block"}
"evaluated
block"
(1
==
1).if_false
{puts
"evaluated
block"}
#
block
is
ignored
(1
==
2).if_true
{puts
"evaluated
block"}
false
class
FalseClass
def
if_true
self
end
def
if_false
yield
self
end
end
Slide 69
Slide 69 text
Jan 2015
@sandimetz
(1
==
1).if_true
{puts
"evaluated
block"}
"evaluated
block"
(1
==
1).if_false
{puts
"evaluated
block"}
#
block
is
ignored
(1
==
2).if_true
{puts
"evaluated
block"}
class
FalseClass
def
if_true
self
end
def
if_false
yield
self
end
end
Slide 70
Slide 70 text
Jan 2015
@sandimetz
(1
==
1).if_true
{puts
"evaluated
block"}
"evaluated
block"
(1
==
1).if_false
{puts
"evaluated
block"}
#
block
is
ignored
(1
==
2).if_true
{puts
"evaluated
block"}
#
block
is
ignored
class
FalseClass
def
if_true
self
end
def
if_false
yield
self
end
end
Slide 71
Slide 71 text
Jan 2015
@sandimetz
(1
==
1).if_true
{puts
"evaluated
block"}
"evaluated
block"
(1
==
1).if_false
{puts
"evaluated
block"}
#
block
is
ignored
(1
==
2).if_true
{puts
"evaluated
block"}
#
block
is
ignored
(1
==
2).if_false
{puts
"evaluated
block"}
class
FalseClass
def
if_true
self
end
def
if_false
yield
self
end
end
Slide 72
Slide 72 text
Jan 2015
@sandimetz
(1
==
1).if_true
{puts
"evaluated
block"}
"evaluated
block"
(1
==
1).if_false
{puts
"evaluated
block"}
#
block
is
ignored
(1
==
2).if_true
{puts
"evaluated
block"}
#
block
is
ignored
(1
==
2).if_false
{puts
"evaluated
block"}
"evaluated
block"
class
FalseClass
def
if_true
self
end
def
if_false
yield
self
end
end
Slide 73
Slide 73 text
Jan 2015
@sandimetz
‘Message sending’ syntax
for
truthy/falsey
Slide 74
Slide 74 text
Jan 2015
@sandimetz
class
TrueClass
def
if_true
yield
self
end
def
if_false
self
end
end
class
FalseClass
def
if_true
self
end
def
if_false
yield
self
end
end
Slide 75
Slide 75 text
Jan 2015
@sandimetz
class
TrueClass
def
if_true
yield
self
end
def
if_false
self
end
end
class
FalseClass
def
if_true
self
end
def
if_false
yield
self
end
end
Slide 76
Slide 76 text
Jan 2015
@sandimetz
class
Object
def
if_true
yield
self
end
def
if_false
self
end
end
class
FalseClass
def
if_true
self
end
def
if_false
yield
self
end
end
Slide 77
Slide 77 text
Jan 2015
@sandimetz
class
Object
def
if_true
yield
self
end
def
if_false
self
end
end
class
FalseClass
def
if_true
self
end
def
if_false
yield
self
end
end
class
NilClass
def
if_true
self
end
def
if_false
yield
self
end
end
Slide 78
Slide 78 text
Jan 2015
@sandimetz
class
Object
def
if_true
yield
self
end
def
if_false
self
end
end
class
FalseClass
def
if_true
self
end
def
if_false
yield
self
end
end
class
NilClass
def
if_true
self
end
def
if_false
yield
self
end
end
* Shamelessly swiped from
http://yehudakatz.com/2009/10/04/emulating-smalltalks-conditionals-in-ruby/
Slide 79
Slide 79 text
Jan 2015
@sandimetz
(1
==
1).if_true
{puts
"evaluated
block"}
Slide 80
Slide 80 text
Jan 2015
@sandimetz
Slide 81
Slide 81 text
Jan 2015
@sandimetz
"anything".if_true
{puts
"evaluated
block"}
Slide 82
Slide 82 text
Jan 2015
@sandimetz
"anything".if_true
{puts
"evaluated
block"}
"evaluated
block"
Slide 83
Slide 83 text
Jan 2015
@sandimetz
"anything".if_true
{puts
"evaluated
block"}
"evaluated
block"
"anything".if_false
{puts
"evaluated
block"}
Slide 84
Slide 84 text
Jan 2015
@sandimetz
"anything".if_true
{puts
"evaluated
block"}
"evaluated
block"
"anything".if_false
{puts
"evaluated
block"}
#
block
is
ignored
Slide 85
Slide 85 text
Jan 2015
@sandimetz
"anything".if_true
{puts
"evaluated
block"}
"evaluated
block"
"anything".if_false
{puts
"evaluated
block"}
#
block
is
ignored
nil.if_true
{puts
"evaluated
block"}
Slide 86
Slide 86 text
Jan 2015
@sandimetz
"anything".if_true
{puts
"evaluated
block"}
"evaluated
block"
"anything".if_false
{puts
"evaluated
block"}
#
block
is
ignored
nil.if_true
{puts
"evaluated
block"}
#
block
is
ignored
Slide 87
Slide 87 text
Jan 2015
@sandimetz
"anything".if_true
{puts
"evaluated
block"}
"evaluated
block"
"anything".if_false
{puts
"evaluated
block"}
#
block
is
ignored
nil.if_true
{puts
"evaluated
block"}
#
block
is
ignored
nil.if_false
{puts
"evaluated
block"}
Slide 88
Slide 88 text
Jan 2015
@sandimetz
"anything".if_true
{puts
"evaluated
block"}
"evaluated
block"
"anything".if_false
{puts
"evaluated
block"}
#
block
is
ignored
nil.if_true
{puts
"evaluated
block"}
#
block
is
ignored
nil.if_false
{puts
"evaluated
block"}
"evaluated
block"
Slide 89
Slide 89 text
Jan 2015
@sandimetz
if
(1
==
1)
puts
'is
true'
else
puts
'is
false'
end
=>
'is
true'
Slide 90
Slide 90 text
Jan 2015
@sandimetz
(1
==
1).
if_true
{puts
'is
true'}.
if_false
{puts
'is
false’}
=>
'is
true'
if
(1
==
1)
puts
'is
true'
else
puts
'is
false'
end
=>
'is
true'
Slide 91
Slide 91 text
Jan 2015
@sandimetz
if
(1
==
2)
puts
'is
true'
else
puts
'is
false'
end
=>
'is
false'
(1
==
1).
if_true
{puts
'is
true'}.
if_false
{puts
'is
false’}
=>
'is
true'
if
(1
==
1)
puts
'is
true'
else
puts
'is
false'
end
=>
'is
true'
Slide 92
Slide 92 text
Jan 2015
@sandimetz
if
(1
==
2)
puts
'is
true'
else
puts
'is
false'
end
=>
'is
false'
(1
==
1).
if_true
{puts
'is
true'}.
if_false
{puts
'is
false’}
=>
'is
true'
if
(1
==
1)
puts
'is
true'
else
puts
'is
false'
end
=>
'is
true'
(1
==
2).
if_true
{puts
'is
true'}.
if_false
{puts
'is
false’}
=>
'is
false'
Slide 93
Slide 93 text
Jan 2015
@sandimetz
I don't want to change Ruby
Slide 94
Slide 94 text
Jan 2015
@sandimetz
I want to change you
Slide 95
Slide 95 text
Jan 2015
@sandimetz
What if there were no 'if' ?
Slide 96
Slide 96 text
Jan 2015
@sandimetz
Smalltalk Infected
Slide 97
Slide 97 text
Jan 2015
@sandimetz
Smalltalk Infected
Slide 98
Slide 98 text
Jan 2015
@sandimetz
Smalltalk Infected
Condition Averse
Slide 99
Slide 99 text
Jan 2015
@sandimetz
Animal.find('pig')
=>
#
Slide 100
Slide 100 text
Jan 2015
@sandimetz
Animal.find('pig')
=>
#
Animal.find('')
=>
nil
Slide 101
Slide 101 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
Slide 102
Slide 102 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
Slide 103
Slide 103 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
Slide 104
Slide 104 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.each
{|animal|
puts
animal.name}
=>
'pig'
NoMethodError:
undefined
method
`name'
for
nil:NilClass
Slide 105
Slide 105 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.each
{|animal|
puts
animal.name}
=>
'pig'
NoMethodError:
undefined
method
`name'
for
nil:NilClass
Slide 106
Slide 106 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.each
{|animal|
puts
animal.name}
=>
'pig'
NoMethodError:
undefined
method
`name'
for
nil:NilClass
Slide 107
Slide 107 text
Jan 2015
@sandimetz
Sometimes nil is nothing
Slide 108
Slide 108 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
Slide 109
Slide 109 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.compact
=>
[#,
#]
Slide 110
Slide 110 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.compact
=>
[#,
#]
animals.each
{|animal|puts
animal.name}
=>
'pig'
'sheep'
Slide 111
Slide 111 text
Jan 2015
@sandimetz
Slide 112
Slide 112 text
Jan 2015
@sandimetz
But if you send it a message
Slide 113
Slide 113 text
Jan 2015
@sandimetz
But if you send it a message
nil is something
Slide 114
Slide 114 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.each
{|animal|
puts
animal.name}
=>
'pig'
NoMethodError:
undefined
method
`name'
for
nil:NilClass
Slide 115
Slide 115 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.each
{|animal|
puts
animal.name}
=>
'pig'
NoMethodError:
undefined
method
`name'
for
nil:NilClass
Slide 116
Slide 116 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.each
{|animal|
puts
animal.nil?
?
'no
animal'
:
animal.name}
=>
'pig'
'no
animal'
'sheep'
Slide 117
Slide 117 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.each
{|animal|
puts
animal.nil?
?
'no
animal'
:
animal.name}
=>
'pig'
'no
animal'
'sheep'
Slide 118
Slide 118 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.each
{|animal|
puts
animal.nil?
?
'no
animal'
:
animal.name}
=>
'pig'
'no
animal'
'sheep'
Slide 119
Slide 119 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.each
{|animal|
puts
animal.nil?
?
'no
animal'
:
animal.name}
=>
'pig'
'no
animal'
'sheep'
Slide 120
Slide 120 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.each
{|animal|
puts
animal.nil?
?
'no
animal'
:
animal.name}
=>
'pig'
'no
animal'
'sheep'
Slide 121
Slide 121 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.each
{|animal|
puts
animal.nil?
?
'no
animal'
:
animal.name}
=>
'pig'
'no
animal'
'sheep'
Slide 122
Slide 122 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.each
{|animal|
puts
animal
&&
animal.name
}
=>
'pig'
empty
string
'sheep'
Slide 123
Slide 123 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.each
{|animal|
puts
animal
&&
animal.name
}
=>
'pig'
empty
string
'sheep'
Slide 124
Slide 124 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.each
{|animal|
puts
animal
&&
animal.name
}
=>
'pig'
empty
string
'sheep'
Slide 125
Slide 125 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.each
{|animal|
puts
animal
&&
animal.name
}
=>
'pig'
empty
string
'sheep'
Slide 126
Slide 126 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.each
{|animal|
puts
animal
&&
animal.name
}
=>
'pig'
empty
string
'sheep'
Slide 127
Slide 127 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.each
{|animal|
puts
animal
&&
animal.name
}
=>
'pig'
empty
string
'sheep'
Slide 128
Slide 128 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.each
{|animal|
puts
animal.try(:name)}
=>
'pig'
empty
string
'sheep'
Slide 129
Slide 129 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.each
{|animal|
puts
animal.try(:name)}
=>
'pig'
empty
string
'sheep'
Slide 130
Slide 130 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.each
{|animal|
puts
animal.try(:name)}
=>
'pig'
empty
string
'sheep'
Slide 131
Slide 131 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.each
{|animal|
puts
animal.try(:name)}
=>
'pig'
empty
string
'sheep'
Slide 132
Slide 132 text
Jan 2015
@sandimetz
puts
animal.try(:name)
puts
animal.nil?
?
''
:
animal.name
puts
animal
==
nil
?
''
:
animal.name
puts
animal.is_a?(NilClass)
?
''
:
animal.name
Slide 133
Slide 133 text
Jan 2015
@sandimetz
puts
animal.try(:name)
puts
animal.nil?
?
''
:
animal.name
puts
animal
==
nil
?
''
:
animal.name
puts
animal.is_a?(NilClass)
?
''
:
animal.name
Slide 134
Slide 134 text
Jan 2015
@sandimetz
puts
animal.try(:name)
puts
animal.nil?
?
''
:
animal.name
puts
animal
==
nil
?
''
:
animal.name
puts
animal.is_a?(NilClass)
?
''
:
animal.name
Slide 135
Slide 135 text
Jan 2015
@sandimetz
puts
animal.try(:name)
puts
animal.nil?
?
''
:
animal.name
puts
animal
==
nil
?
''
:
animal.name
puts
animal.is_a?(NilClass)
?
''
:
animal.name
Slide 136
Slide 136 text
Jan 2015
@sandimetz
puts
animal.is_a?(NilClass)
?
''
:
animal.name
if
animal.is_a?(NilClass)
puts
''
else
puts
animal.name
end
Slide 137
Slide 137 text
Jan 2015
@sandimetz
puts
animal.is_a?(NilClass)
?
''
:
animal.name
if
animal.is_a?(NilClass)
puts
''
else
puts
animal.name
end
Slide 138
Slide 138 text
Jan 2015
@sandimetz
if
animal.is_a?(NilClass)
puts
''
else
puts
animal.name
end
Slide 139
Slide 139 text
Jan 2015
@sandimetz
if
animal.is_a?(NilClass)
puts
''
else
puts
animal.name
end
Slide 140
Slide 140 text
Jan 2015
@sandimetz
if
animal.is_a?(NilClass)
puts
''
else
puts
animal.name
end
Slide 141
Slide 141 text
Jan 2015
@sandimetz
if
(some
object
whose
type
I
know)
code
to
do
some
stuff
else
code
to
do
some
other
stuff
end
if
animal.is_a?(NilClass)
puts
'no
animal'
else
puts
animal.name
end
Slide 142
Slide 142 text
Jan 2015
@sandimetz
if
(some
object
whose
type
I
know)
code
to
do
some
stuff
else
code
to
do
some
other
stuff
end
if
animal.is_a?(NilClass)
puts
'no
animal'
else
puts
animal.name
end
Slide 143
Slide 143 text
Jan 2015
@sandimetz
if
(some
object
whose
type
I
know)
code
to
do
some
stuff
else
code
to
do
some
other
stuff
end
if
animal.is_a?(NilClass)
puts
'no
animal'
else
puts
animal.name
end
Slide 144
Slide 144 text
Jan 2015
@sandimetz
if
(some
object
whose
type
I
know)
I'll
supply
the
behavior
else
code
to
do
some
other
stuff
end
if
animal.is_a?(NilClass)
puts
'no
animal'
else
puts
animal.name
end
Slide 145
Slide 145 text
Jan 2015
@sandimetz
if
(some
object
whose
type
I
know)
I'll
supply
the
behavior
else
code
to
do
some
other
stuff
end
if
animal.is_a?(NilClass)
puts
'no
animal'
else
puts
animal.name
end
Slide 146
Slide 146 text
Jan 2015
@sandimetz
if
(some
object
whose
type
I
know)
I'll
supply
the
behavior
else
code
to
do
some
other
stuff
end
if
animal.is_a?(NilClass)
puts
'no
animal'
else
puts
animal.name
end
Slide 147
Slide 147 text
Jan 2015
@sandimetz
if
animal.is_a?(NilClass)
puts
'no
animal'
else
puts
animal.name
end
if
(some
object
whose
type
I
know)
I'll
supply
the
behavior
else
I'll
send
a
message
end
Slide 148
Slide 148 text
Jan 2015
@sandimetz
Slide 149
Slide 149 text
Jan 2015
@sandimetz
conditions
Slide 150
Slide 150 text
Jan 2015
@sandimetz
conditions
breed
Slide 151
Slide 151 text
Jan 2015
@sandimetz
class
Animal
def
self.find
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
Slide 152
Slide 152 text
Jan 2015
@sandimetz
class
Animal
def
self.find
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
Slide 153
Slide 153 text
Jan 2015
@sandimetz
class
Animal
def
self.find
ind(id)
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
Animal.find(id)
?
'no
animal'
:
animal.name
Slide 154
Slide 154 text
Jan 2015
@sandimetz
class
Animal
def
self.find
ind(id)
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
Animal.find(id)
?
'no
animal'
:
animal.name
find(id)
animal'
:
animal.name
d)
imal'
:
animal.name
Slide 155
Slide 155 text
Jan 2015
@sandimetz
class
Animal
def
self.find
ind(id)
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
Animal.find(id)
?
'no
animal'
:
animal.name
find(id)
animal'
:
animal.name
d)
imal'
:
animal.name
'no
animal'
Slide 156
Slide 156 text
Jan 2015
@sandimetz
class
Animal
def
self.find
ind(id)
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
Animal.find(id)
?
'no
animal'
:
animal.name
find(id)
animal'
:
animal.name
d)
imal'
:
animal.name
'no
animal'
'no
animal'
Slide 157
Slide 157 text
Jan 2015
@sandimetz
class
Animal
def
self.find
ind(id)
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
Animal.find(id)
?
'no
animal'
:
animal.name
find(id)
animal'
:
animal.name
d)
imal'
:
animal.name
'no
animal'
'no
animal'
'no
animal'
Slide 158
Slide 158 text
Jan 2015
@sandimetz
class
Animal
def
self.find
ind(id)
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
Animal.find(id)
?
'no
animal'
:
animal.name
find(id)
animal'
:
animal.name
d)
imal'
:
animal.name
'no
animal'
'no
animal'
'no
animal'
'no
animal'
Slide 159
Slide 159 text
Jan 2015
@sandimetz
class
Animal
def
self.find
ind(id)
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
animal
=
Animal.find(id)
animal.nil?
?
'no
animal'
:
animal.name
Animal.find(id)
?
'no
animal'
:
animal.name
find(id)
animal'
:
animal.name
d)
imal'
:
animal.name
'no
animal'
'no
animal'
'no
animal'
'no
animal'
'no
animal'
!!!!
Slide 160
Slide 160 text
Jan 2015
@sandimetz
Change?
Slide 161
Slide 161 text
Jan 2015
@sandimetz
Shotgun
Surgery
Slide 162
Slide 162 text
Jan 2015
@sandimetz
Shotgun
Surgery
Slide 163
Slide 163 text
Jan 2015
@sandimetz
Smalltalk Infected
Condition Averse
Slide 164
Slide 164 text
Jan 2015
@sandimetz
Smalltalk Infected
Condition Averse
Message Centric
Slide 165
Slide 165 text
Jan 2015
@sandimetz
if
animal.is_a?(NilClass)
puts
'no
animal'
else
puts
animal.name
end
if
(some
object
whose
type
I
know)
I'll
supply
the
behavior
else
I'll
send
a
message
end
Slide 166
Slide 166 text
Jan 2015
@sandimetz
if
animal.is_a?(NilClass)
puts
'no
animal'
else
puts
animal.name
end
Slide 167
Slide 167 text
Jan 2015
@sandimetz
if
animal.is_a?(NilClass)
puts
'no
animal'
else
puts
animal.name
end
Slide 168
Slide 168 text
Jan 2015
@sandimetz
class
Animal
def
name
...
end
end
Slide 169
Slide 169 text
Jan 2015
@sandimetz
class
Animal
def
name
...
end
end
class
Nil
#
does
not
understand
name
end
Slide 170
Slide 170 text
Jan 2015
@sandimetz
class
Animal
def
name
...
end
end
class
???
def
name
'no
animal'
end
end
Slide 171
Slide 171 text
Jan 2015
@sandimetz
class
Animal
def
name
...
end
end
class
MissingAnimal
def
name
'no
animal'
end
end
Slide 172
Slide 172 text
Jan 2015
@sandimetz
Prefer knowing an object
to duplicating behavior
Slide 173
Slide 173 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)}
=>
[#,
nil,
#]
animals.each
{|animal|
if
animal.is_a?(NilClass)
puts
'no
animal'
else
puts
animal.name
end
}
Slide 174
Slide 174 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)
||
MissingAnimal.new}
=>
[#,
nil,
#]
animals.each
{|animal|
if
animal.is_a?(NilClass)
puts
'no
animal'
else
puts
animal.name
end
}
Slide 175
Slide 175 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)
||
MissingAnimal.new}
=>
[#,
nil,
#]
animals.each
{|animal|
if
animal.is_a?(NilClass)
puts
'no
animal'
else
puts
animal.name
end
}
Slide 176
Slide 176 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)
||
MissingAnimal.new}
=>
[#,
nil,
#]
animals.each
{|animal|
if
animal.is_a?(NilClass)
puts
'no
animal'
else
puts
animal.name
end
}
Slide 177
Slide 177 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)
||
MissingAnimal.new}
=>
[#,
#,
#]
animals.each
{|animal|
if
animal.is_a?(NilClass)
puts
'no
animal'
else
puts
animal.name
end
}
Slide 178
Slide 178 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)
||
MissingAnimal.new}
=>
[#,
#,
#]
animals.each
{|animal|
if
animal.is_a?(NilClass)
puts
'no
animal'
else
puts
animal.name
end
}
added dependency
Slide 179
Slide 179 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)
||
MissingAnimal.new}
=>
[#,
#,
#]
animals.each
{|animal|
if
animal.is_a?(NilClass)
puts
'no
animal'
else
puts
animal.name
end
}
Slide 180
Slide 180 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)
||
MissingAnimal.new}
=>
[#,
#,
#]
animals.each
{|animal|
if
animal.is_a?(NilClass)
puts
'no
animal'
else
puts
animal.name
end
}
still have the condition
Slide 181
Slide 181 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)
||
MissingAnimal.new}
=>
[#,
#,
#]
animals.each
{|animal|
if
animal.is_a?(NilClass)
puts
'no
animal'
else
puts
animal.name
end
}
but no longer
own the behavior
Slide 182
Slide 182 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)
||
MissingAnimal.new}
=>
[#,
#,
#]
animals.each
{|animal|
if
animal.is_a?(NilClass)
puts
'no
animal'
else
puts
animal.name
end
}
Slide 183
Slide 183 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)
||
MissingAnimal.new}
=>
[#,
#,
#]
animals.each
{|animal|
puts
animal.name
}
Slide 184
Slide 184 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)
||
MissingAnimal.new}
=>
[#,
#,
#]
animals.each
{|animal|
puts
animal.name
}
Slide 185
Slide 185 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)
||
MissingAnimal.new}
=>
[#,
#,
#]
animals.each
{|animal|
puts
animal.name}
Slide 186
Slide 186 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)
||
MissingAnimal.new}
=>
[#,
#,
#]
animals.each
{|animal|
puts
animal.name}
=>
'pig'
'no
animal'
'sheep'
Slide 187
Slide 187 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)
||
MissingAnimal.new}
=>
[#,
#,
#]
animals.each
{|animal|
puts
animal.name}
=>
'pig'
'no
animal'
'sheep'
Slide 188
Slide 188 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)
||
MissingAnimal.new}
=>
[#,
#,
#]
animals.each
{|animal|
puts
animal.name}
=>
'pig'
'no
animal'
'sheep'
Slide 189
Slide 189 text
Jan 2015
@sandimetz
class
Animal
def
name
...
end
end
class
MissingAnimal
def
name
'no
animal'
end
end
Slide 190
Slide 190 text
Jan 2015
@sandimetz
Slide 191
Slide 191 text
Jan 2015
@sandimetz
Null Object Pattern
Slide 192
Slide 192 text
Jan 2015
@sandimetz
Null Object Pattern
'Active Nothing'
Slide 193
Slide 193 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)
||
MissingAnimal.new}
animals.each
{|animal|
puts
animal.name}
=>
'pig'
'no
animal'
'sheep'
Slide 194
Slide 194 text
Jan 2015
@sandimetz
ids
=
['pig',
'',
'sheep']
animals
=
ids.map
{|id|
Animal.find(id)
||
MissingAnimal.new}
animals.each
{|animal|
puts
animal.name}
=>
'pig'
'no
animal'
'sheep'
dependency
Slide 195
Slide 195 text
Jan 2015
@sandimetz
Prefer knowing an object
to duplicating behavior
Slide 196
Slide 196 text
Jan 2015
@sandimetz
Prefer knowing
few objects
Slide 197
Slide 197 text
Jan 2015
@sandimetz
class
Animal
def
self.find
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
Slide 198
Slide 198 text
Jan 2015
@sandimetz
class
Animal
def
self.find
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
Slide 199
Slide 199 text
Jan 2015
@sandimetz
class
Animal
def
self.find
||
MissingAnimal.new
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
al.find(id)
||
MissingAnimal.new
Slide 200
Slide 200 text
Jan 2015
@sandimetz
class
Animal
def
self.find
||
MissingAnimal.new
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
al.find(id)
||
MissingAnimal.new
)
||
MissingAnimal.new
issingAnimal.new
Slide 201
Slide 201 text
Jan 2015
@sandimetz
class
Animal
def
self.find
||
MissingAnimal.new
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
al.find(id)
||
MissingAnimal.new
)
||
MissingAnimal.new
issingAnimal.new
MissingAnimal
Slide 202
Slide 202 text
Jan 2015
@sandimetz
class
Animal
def
self.find
||
MissingAnimal.new
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
al.find(id)
||
MissingAnimal.new
)
||
MissingAnimal.new
issingAnimal.new
MissingAnimal
MissingAnimal
Slide 203
Slide 203 text
Jan 2015
@sandimetz
class
Animal
def
self.find
||
MissingAnimal.new
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
al.find(id)
||
MissingAnimal.new
)
||
MissingAnimal.new
issingAnimal.new
MissingAnimal
MissingAnimal
MissingAnimal
Slide 204
Slide 204 text
Jan 2015
@sandimetz
class
Animal
def
self.find
||
MissingAnimal.new
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
al.find(id)
||
MissingAnimal.new
)
||
MissingAnimal.new
issingAnimal.new
MissingAnimal
MissingAnimal
MissingAnimal
MissingAnimal
Slide 205
Slide 205 text
Jan 2015
@sandimetz
class
Animal
def
self.find
||
MissingAnimal.new
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
animal
=
Animal.find(id)
||
MissingAnimal.new
animal.name
al.find(id)
||
MissingAnimal.new
)
||
MissingAnimal.new
issingAnimal.new
MissingAnimal
MissingAnimal
MissingAnimal
MissingAnimal
MissingAnimal
???
Slide 206
Slide 206 text
Jan 2015
@sandimetz
class
Animal
def
self.find(id)
#
nil
or
an
Animal
end
#
…
end
Slide 207
Slide 207 text
Jan 2015
@sandimetz
class
Animal
def
self.find
Slide 208
Slide 208 text
Jan 2015
@sandimetz
class
GuaranteedAnimal
def
self.find
class
Animal
def
self.find
Slide 209
Slide 209 text
Jan 2015
@sandimetz
class
GuaranteedAnimal
def
self.find
class
Animal
def
self.find
class
GuaranteedAnimal
def
self.find(id)
Animal.find(id)
||
MissingAnimal.new
end
end
Slide 210
Slide 210 text
Jan 2015
@sandimetz
animals
=
ids.map
{|id|Animal.find(id)||MissingAnimal.new}
Slide 211
Slide 211 text
Jan 2015
@sandimetz
animals
=
ids.map
{|id|Animal.find(id)||MissingAnimal.new}
Slide 212
Slide 212 text
Jan 2015
@sandimetz
animals
=
ids.map
{|id|
GuaranteedAnimal.find(id)}
=>
[#,
#,
#]
Slide 213
Slide 213 text
Jan 2015
@sandimetz
animals
=
ids.map
{|id|
GuaranteedAnimal.find(id)}
=>
[#,
#,
#]
Slide 214
Slide 214 text
Jan 2015
@sandimetz
animals
=
ids.map
{|id|
GuaranteedAnimal.find(id)}
=>
[#,
#,
#]
animals.each
{|animal|
puts
animal.name
}
=>
'pig'
'no
animal'
'sheep'
Slide 215
Slide 215 text
Jan 2015
@sandimetz
animals
=
ids.map
{|id|
GuaranteedAnimal.find(id)}
=>
[#,
#,
#]
animals.each
{|animal|
puts
animal.name
}
=>
'pig'
'no
animal'
'sheep'
Slide 216
Slide 216 text
Jan 2015
@sandimetz
animals
=
ids.map
{|id|
GuaranteedAnimal.find(id)}
=>
[#,
#,
#]
animals.each
{|animal|
puts
animal.name
}
=>
'pig'
'no
animal'
'sheep'
Slide 217
Slide 217 text
Jan 2015
@sandimetz
Smalltalk Infected
Condition Averse
Message Centric
Slide 218
Slide 218 text
Jan 2015
@sandimetz
Smalltalk Infected
Condition Averse
Message Centric
Abstraction Seeking
Slide 219
Slide 219 text
Jan 2015
@sandimetz
'This
is
the
house
that
Jack
built.'
1
Slide 220
Slide 220 text
Jan 2015
@sandimetz
'This
is
the
house
that
Jack
built.'
'This
is
the
malt
that
lay
in
the
house
that
Jack
built.'
1
2
Slide 221
Slide 221 text
Jan 2015
@sandimetz
'This
is
the
house
that
Jack
built.'
'This
is
the
malt
that
lay
in
the
house
that
Jack
built.'
'This
is
the
rat
that
ate
the
malt
that
lay
in
the
house
that
Jack
built.'
1
2
3
Slide 222
Slide 222 text
Jan 2015
@sandimetz
'This
is
the
house
that
Jack
built.'
'This
is
the
malt
that
lay
in
the
house
that
Jack
built.'
'This
is
the
rat
that
ate
the
malt
that
lay
in
the
house
that
Jack
built.'
'This
is
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
farmer
sowing
his
corn
that
kept
the
rooster
that
crowed
in
the
morn
that
woke
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
maiden
all
forlorn
that
milked
the
cow
with
the
crumpled
horn
that
tossed
the
dog
that
worried
the
cat
that
killed
the
rat
that
ate
the
malt
that
lay
in
the
house
that
Jack
built.'
12
Slide 223
Slide 223 text
Jan 2015
@sandimetz
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
'the
farmer
sowing
his
corn
that
kept',
'the
rooster
that
crowed
in
the
morn
that
woke',
'the
priest
all
shaven
and
shorn
that
married',
'the
man
all
tattered
and
torn
that
kissed',
'the
maiden
all
forlorn
that
milked',
'the
cow
with
the
crumpled
horn
that
tossed',
'the
dog
that
worried',
'the
cat
that
killed',
'the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built'
]
Slide 224
Slide 224 text
Jan 2015
@sandimetz
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
'the
farmer
sowing
his
corn
that
kept',
'the
rooster
that
crowed
in
the
morn
that
woke',
'the
priest
all
shaven
and
shorn
that
married',
'the
man
all
tattered
and
torn
that
kissed',
'the
maiden
all
forlorn
that
milked',
'the
cow
with
the
crumpled
horn
that
tossed',
'the
dog
that
worried',
'the
cat
that
killed',
'the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
Slide 225
Slide 225 text
Jan 2015
@sandimetz
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
'the
farmer
sowing
his
corn
that
kept',
'the
rooster
that
crowed
in
the
morn
that
woke',
'the
priest
all
shaven
and
shorn
that
married',
'the
man
all
tattered
and
torn
that
kissed',
'the
maiden
all
forlorn
that
milked',
'the
cow
with
the
crumpled
horn
that
tossed',
'the
dog
that
worried',
'the
cat
that
killed',
'the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
Slide 226
Slide 226 text
Jan 2015
@sandimetz
def
phrase(number)
data.last(number).join("
")
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
'the
farmer
sowing
his
corn
that
kept',
'the
rooster
that
crowed
in
the
morn
that
woke',
'the
priest
all
shaven
and
shorn
that
married',
'the
man
all
tattered
and
torn
that
kissed',
'the
maiden
all
forlorn
that
milked',
'the
cow
with
the
crumpled
horn
that
tossed',
'the
dog
that
worried',
'the
cat
that
killed',
'the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
Slide 227
Slide 227 text
Jan 2015
@sandimetz
def
phrase(number)
data.last(number).join("
")
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
'the
farmer
sowing
his
corn
that
kept',
'the
rooster
that
crowed
in
the
morn
that
woke',
'the
priest
all
shaven
and
shorn
that
married',
'the
man
all
tattered
and
torn
that
kissed',
'the
maiden
all
forlorn
that
milked',
'the
cow
with
the
crumpled
horn
that
tossed',
'the
dog
that
worried',
'the
cat
that
killed',
'the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
data.last(3)
=>
['the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
Slide 228
Slide 228 text
Jan 2015
@sandimetz
def
phrase(number)
data.last(number).join("
")
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
Slide 229
Slide 229 text
Jan 2015
@sandimetz
def
phrase(number)
data.last(number).join("
")
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
Slide 230
Slide 230 text
Jan 2015
@sandimetz
def
phrase(number)
data.last(number).join("
")
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
Slide 231
Slide 231 text
Jan 2015
@sandimetz
def
line(number)
"This
is
#{phrase(number)}.\n"
end
def
phrase(number)
data.last(number).join("
")
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
Slide 232
Slide 232 text
Jan 2015
@sandimetz
def
line(number)
"This
is
#{phrase(number)}.\n"
end
def
phrase(number)
data.last(number).join("
")
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
Slide 233
Slide 233 text
Jan 2015
@sandimetz
def
recite
(1..data.length).map
{|i|
line(i)}.join("\n")
end
def
line(number)
"This
is
#{phrase(number)}.\n"
end
def
phrase(number)
data.last(number).join("
")
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
Slide 234
Slide 234 text
Jan 2015
@sandimetz
def
recite
(1..data.length).map
{|i|
line(i)}.join("\n")
end
def
line(number)
"This
is
#{phrase(number)}.\n"
end
def
phrase(number)
data.last(number).join("
")
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
Slide 235
Slide 235 text
Jan 2015
@sandimetz
class
House
def
recite
(1..data.length).map
{|i|
line(i)}.join("\n")
end
def
line(number)
"This
is
#{phrase(number)}.\n"
end
def
phrase(number)
data.last(number).join("
")
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
Slide 236
Slide 236 text
Jan 2015
@sandimetz
Slide 237
Slide 237 text
Jan 2015
@sandimetz
puts
House.new.line(1)
=>
'This
is
the
house
that
Jack
built.'
Slide 238
Slide 238 text
Jan 2015
@sandimetz
puts
House.new.line(1)
=>
'This
is
the
house
that
Jack
built.'
puts
House.new.line(2)
=>
'This
is
the
malt
that
lay
in
the
house
that
Jack
built.'
Slide 239
Slide 239 text
Jan 2015
@sandimetz
puts
House.new.line(1)
=>
'This
is
the
house
that
Jack
built.'
puts
House.new.line(2)
=>
'This
is
the
malt
that
lay
in
the
house
that
Jack
built.'
puts
House.new.line(3)
=>
'This
is
the
rat
that
ate
the
malt
that
lay
in
the
house
that
Jack
built.'
Slide 240
Slide 240 text
Jan 2015
@sandimetz
puts
House.new.line(1)
=>
'This
is
the
house
that
Jack
built.'
puts
House.new.line(2)
=>
'This
is
the
malt
that
lay
in
the
house
that
Jack
built.'
puts
House.new.line(3)
=>
'This
is
the
rat
that
ate
the
malt
that
lay
in
the
house
that
Jack
built.'
puts
House.new.line(12)
=>
'This
is
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
farmer
sowing
his
corn
that
kept
the
rooster
that
crowed
in
the
morn
that
woke
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
maiden
all
forlorn
that
milked
the
cow
with
the
crumpled
horn
that
tossed
the
dog
that
worried
the
cat
that
killed
the
rat
that
ate
the
malt
that
lay
in
the
house
that
Jack
built.'
Slide 241
Slide 241 text
Jan 2015
@sandimetz
puts
House.new.line(1)
=>
'This
is
the
house
that
Jack
built.'
puts
House.new.line(2)
=>
'This
is
the
malt
that
lay
in
the
house
that
Jack
built.'
puts
House.new.line(3)
=>
'This
is
the
rat
that
ate
the
malt
that
lay
in
the
house
that
Jack
built.'
puts
House.new.line(12)
=>
'This
is
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
farmer
sowing
his
corn
that
kept
the
rooster
that
crowed
in
the
morn
that
woke
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
maiden
all
forlorn
that
milked
the
cow
with
the
crumpled
horn
that
tossed
the
dog
that
worried
the
cat
that
killed
the
rat
that
ate
the
malt
that
lay
in
the
house
that
Jack
built.'
puts
House.new.recite
=>
'This
is
the
house
that
Jack
built.'
'This
is
the
malt
that
lay
in
the
house
that
Jack
built.'
'This
is
the
rat
that
ate
the
malt
that
lay
in
the
house
that
Jack
built.'
etc
Slide 242
Slide 242 text
Jan 2015
@sandimetz
Slide 243
Slide 243 text
Jan 2015
@sandimetz
New Feature Request:
Slide 244
Slide 244 text
Jan 2015
@sandimetz
New Feature Request:
RandomHouse
Slide 245
Slide 245 text
Jan 2015
@sandimetz
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
'the
farmer
sowing
his
corn
that
kept',
'the
rooster
that
crowed
in
the
morn
that
woke',
'the
priest
all
shaven
and
shorn
that
married',
'the
man
all
tattered
and
torn
that
kissed',
'the
maiden
all
forlorn
that
milked',
'the
cow
with
the
crumpled
horn
that
tossed',
'the
dog
that
worried',
'the
cat
that
killed',
'the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built'
]
Slide 246
Slide 246 text
Jan 2015
@sandimetz
[
'the
rooster
that
crowed
in
the
morn
that
woke',
'the
farmer
sowing
his
corn
that
kept',
'the
dog
that
worried',
'the
priest
all
shaven
and
shorn
that
married',
'the
man
all
tattered
and
torn
that
kissed',
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
'the
malt
that
lay
in',
'the
cow
with
the
crumpled
horn
that
tossed',
'the
house
that
Jack
built',
'the
cat
that
killed',
'the
maiden
all
forlorn
that
milked',
'the
rat
that
ate']
Slide 247
Slide 247 text
Jan 2015
@sandimetz
[
'the
rooster
that
crowed
in
the
morn
that
woke',
'the
farmer
sowing
his
corn
that
kept',
'the
dog
that
worried',
'the
priest
all
shaven
and
shorn
that
married',
'the
man
all
tattered
and
torn
that
kissed',
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
'the
malt
that
lay
in',
'the
cow
with
the
crumpled
horn
that
tossed',
'the
house
that
Jack
built',
'the
cat
that
killed',
'the
maiden
all
forlorn
that
milked',
'the
rat
that
ate']
Slide 248
Slide 248 text
Jan 2015
@sandimetz
[
'the
rooster
that
crowed
in
the
morn
that
woke',
'the
farmer
sowing
his
corn
that
kept',
'the
dog
that
worried',
'the
priest
all
shaven
and
shorn
that
married',
'the
man
all
tattered
and
torn
that
kissed',
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
'the
malt
that
lay
in',
'the
cow
with
the
crumpled
horn
that
tossed',
'the
house
that
Jack
built',
'the
cat
that
killed',
'the
maiden
all
forlorn
that
milked',
'the
rat
that
ate']
Slide 249
Slide 249 text
Jan 2015
@sandimetz
[
'the
rooster
that
crowed
in
the
morn
that
woke',
'the
farmer
sowing
his
corn
that
kept',
'the
dog
that
worried',
'the
priest
all
shaven
and
shorn
that
married',
'the
man
all
tattered
and
torn
that
kissed',
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
'the
malt
that
lay
in',
'the
cow
with
the
crumpled
horn
that
tossed',
'the
house
that
Jack
built',
'the
cat
that
killed',
'the
maiden
all
forlorn
that
milked',
'the
rat
that
ate']
Slide 250
Slide 250 text
Jan 2015
@sandimetz
'This
is
the
rat
that
ate.'
1
Slide 251
Slide 251 text
Jan 2015
@sandimetz
'This
is
the
rat
that
ate.'
'This
is
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
1
2
Slide 252
Slide 252 text
Jan 2015
@sandimetz
'This
is
the
rat
that
ate.'
'This
is
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
'This
is
the
cat
that
killed
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
1
2
3
Slide 253
Slide 253 text
Jan 2015
@sandimetz
'This
is
the
rat
that
ate.'
'This
is
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
'This
is
the
cat
that
killed
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
'This
is
the
rooster
that
crowed
in
the
morn
that
woke
the
farmer
sowing
his
corn
that
kept
the
dog
that
worried
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
malt
that
lay
in
the
cow
with
the
crumpled
horn
that
tossed
the
house
that
Jack
built
the
cat
that
killed
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
12
Slide 254
Slide 254 text
Jan 2015
@sandimetz
'This
is
the
rat
that
ate.'
'This
is
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
'This
is
the
cat
that
killed
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
'This
is
the
rooster
that
crowed
in
the
morn
that
woke
the
farmer
sowing
his
corn
that
kept
the
dog
that
worried
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
malt
that
lay
in
the
cow
with
the
crumpled
horn
that
tossed
the
house
that
Jack
built
the
cat
that
killed
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
12
Slide 255
Slide 255 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
Slide 256
Slide 256 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
Task:
Implement RandomHouse
without 'if' statements
Slide 257
Slide 257 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
Inheritance?
Slide 258
Slide 258 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
Slide 259
Slide 259 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
Slide 260
Slide 260 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
Slide 261
Slide 261 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
Slide 262
Slide 262 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
Slide 263
Slide 263 text
Jan 2015
@sandimetz
Slide 264
Slide 264 text
Jan 2015
@sandimetz
randomhouse
=
RandomHouse.new
Slide 265
Slide 265 text
Jan 2015
@sandimetz
randomhouse
=
RandomHouse.new
puts
randomhouse.line(1)
=>
'This
is
the
rat
that
ate.'
Slide 266
Slide 266 text
Jan 2015
@sandimetz
randomhouse
=
RandomHouse.new
puts
randomhouse.line(1)
=>
'This
is
the
rat
that
ate.'
puts
randomhouse.line(2)
=>
'This
is
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
Slide 267
Slide 267 text
Jan 2015
@sandimetz
randomhouse
=
RandomHouse.new
puts
randomhouse.line(1)
=>
'This
is
the
rat
that
ate.'
puts
randomhouse.line(2)
=>
'This
is
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
puts
randomhouse.line(3)
=>
'This
is
the
cat
that
killed
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
Slide 268
Slide 268 text
Jan 2015
@sandimetz
randomhouse
=
RandomHouse.new
puts
randomhouse.line(1)
=>
'This
is
the
rat
that
ate.'
puts
randomhouse.line(2)
=>
'This
is
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
puts
randomhouse.line(3)
=>
'This
is
the
cat
that
killed
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
puts
randomhouse.line(12)
=>
'This
is
the
rooster
that
crowed
in
the
morn
that
woke
the
farmer
sowing
his
corn
that
kept
the
dog
that
worried
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
malt
that
lay
in
the
cow
with
the
crumpled
horn
that
tossed
the
house
that
Jack
built
the
cat
that
killed
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
Slide 269
Slide 269 text
Jan 2015
@sandimetz
randomhouse
=
RandomHouse.new
puts
randomhouse.line(1)
=>
'This
is
the
rat
that
ate.'
puts
randomhouse.line(2)
=>
'This
is
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
puts
randomhouse.line(3)
=>
'This
is
the
cat
that
killed
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
puts
randomhouse.line(12)
=>
'This
is
the
rooster
that
crowed
in
the
morn
that
woke
the
farmer
sowing
his
corn
that
kept
the
dog
that
worried
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
malt
that
lay
in
the
cow
with
the
crumpled
horn
that
tossed
the
house
that
Jack
built
the
cat
that
killed
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
Slide 270
Slide 270 text
Jan 2015
@sandimetz
randomhouse
=
RandomHouse.new
puts
randomhouse.line(1)
=>
'This
is
the
rat
that
ate.'
puts
randomhouse.line(2)
=>
'This
is
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
puts
randomhouse.line(3)
=>
'This
is
the
cat
that
killed
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
puts
randomhouse.line(12)
=>
'This
is
the
rooster
that
crowed
in
the
morn
that
woke
the
farmer
sowing
his
corn
that
kept
the
dog
that
worried
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
malt
that
lay
in
the
cow
with
the
crumpled
horn
that
tossed
the
house
that
Jack
built
the
cat
that
killed
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
Slide 271
Slide 271 text
Jan 2015
@sandimetz
randomhouse
=
RandomHouse.new
puts
randomhouse.line(1)
=>
'This
is
the
rat
that
ate.'
puts
randomhouse.line(2)
=>
'This
is
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
puts
randomhouse.line(3)
=>
'This
is
the
cat
that
killed
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
puts
randomhouse.line(12)
=>
'This
is
the
rooster
that
crowed
in
the
morn
that
woke
the
farmer
sowing
his
corn
that
kept
the
dog
that
worried
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
malt
that
lay
in
the
cow
with
the
crumpled
horn
that
tossed
the
house
that
Jack
built
the
cat
that
killed
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
Slide 272
Slide 272 text
Jan 2015
@sandimetz
Slide 273
Slide 273 text
Jan 2015
@sandimetz
New Feature Request:
Slide 274
Slide 274 text
Jan 2015
@sandimetz
New Feature Request:
EchoHouse
Slide 275
Slide 275 text
Jan 2015
@sandimetz
Slide 276
Slide 276 text
Jan 2015
@sandimetz
This
is
the
house
that
Jack
built
the
house
that
Jack
built.
Slide 277
Slide 277 text
Jan 2015
@sandimetz
This
is
the
house
that
Jack
built
the
house
that
Jack
built.
Slide 278
Slide 278 text
Jan 2015
@sandimetz
This
is
the
house
that
Jack
built
the
house
that
Jack
built.
This
is
the
malt
that
lay
in
the
malt
that
lay
in
the
house
that
Jack
built
the
house
that
Jack
built.
Slide 279
Slide 279 text
Jan 2015
@sandimetz
This
is
the
house
that
Jack
built
the
house
that
Jack
built.
This
is
the
malt
that
lay
in
the
malt
that
lay
in
the
house
that
Jack
built
the
house
that
Jack
built.
Slide 280
Slide 280 text
Jan 2015
@sandimetz
This
is
the
house
that
Jack
built
the
house
that
Jack
built.
This
is
the
malt
that
lay
in
the
malt
that
lay
in
the
house
that
Jack
built
the
house
that
Jack
built.
This
is
the
rat
that
ate
the
rat
that
ate
the
malt
that
lay
in
the
malt
that
lay
in
the
house
that
Jack
built
the
house
that
Jack
built.
Slide 281
Slide 281 text
Jan 2015
@sandimetz
class
House
def
recite
(1..data.length).map
{|i|
line(i)}.join("\n")
end
def
line(number)
"This
is
#{phrase(number)}.\n"
end
def
phrase(number)
data.last(number).join("
")
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
Slide 282
Slide 282 text
Jan 2015
@sandimetz
class
House
def
recite
(1..data.length).map
{|i|
line(i)}.join("\n")
end
def
line(number)
"This
is
#{phrase(number)}.\n"
end
def
phrase(number)
data.last(number).join("
")
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
Slide 283
Slide 283 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
data.last(number).join("
")
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
Slide 284
Slide 284 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
data.last(number).join("
")
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
Slide 285
Slide 285 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
data.last(number).join("
")
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
Slide 286
Slide 286 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
data.last(number).join("
")
end
def
parts(number)
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
Slide 287
Slide 287 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
data.last(number).join("
")
end
def
parts(number)
data.last(number)
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
Slide 288
Slide 288 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
parts(number).join("
")
end
def
parts(number)
data.last(number)
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
Slide 289
Slide 289 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
parts(number).join("
")
end
def
parts(number)
data.last(number)
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
Slide 290
Slide 290 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
def
parts(number)
data.last(number)
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
Slide 291
Slide 291 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
def
parts(number)
data.last(number)
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
['the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
have
Slide 292
Slide 292 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
def
parts(number)
data.last(number)
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
['the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
['the
rat
that
ate',
'the
rat
that
ate',
'the
malt
that
lay
in',
'the
malt
that
lay
in',
'the
house
that
Jack
built',
'the
house
that
Jack
built']
want
Slide 293
Slide 293 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
def
parts(number)
data.last(number)
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
Slide 294
Slide 294 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
def
parts(number)
data.last(number)
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
Task:
Implement EchoHouse
without 'if' statements
Slide 295
Slide 295 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
def
parts(number)
data.last(number)
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
Inheritance?
Slide 296
Slide 296 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
def
parts(number)
data.last(number)
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
Slide 297
Slide 297 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
def
parts(number)
data.last(number)
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
Slide 298
Slide 298 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
def
parts(number)
data.last(number)
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
Slide 299
Slide 299 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
def
parts(number)
data.last(number)
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
Slide 300
Slide 300 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
def
parts(number)
data.last(number)
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
Slide 301
Slide 301 text
Jan 2015
@sandimetz
['the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
Slide 302
Slide 302 text
Jan 2015
@sandimetz
['the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
['the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
Slide 303
Slide 303 text
Jan 2015
@sandimetz
['the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
['the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
super.zip(super)
Slide 304
Slide 304 text
Jan 2015
@sandimetz
['the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
['the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
[['the
rat
that
ate','the
rat
that
ate'],
['the
malt
that
lay
in','the
malt
that
lay
in'],
['the
house
that
Jack
built','the
house
that
Jack
built']]
super.zip(super)
Slide 305
Slide 305 text
Jan 2015
@sandimetz
['the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
super.zip(super).flatten
['the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
[['the
rat
that
ate','the
rat
that
ate'],
['the
malt
that
lay
in','the
malt
that
lay
in'],
['the
house
that
Jack
built','the
house
that
Jack
built']]
super.zip(super)
Slide 306
Slide 306 text
Jan 2015
@sandimetz
['the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
super.zip(super).flatten
['the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
[['the
rat
that
ate','the
rat
that
ate'],
['the
malt
that
lay
in','the
malt
that
lay
in'],
['the
house
that
Jack
built','the
house
that
Jack
built']]
super.zip(super)
['the
rat
that
ate','the
rat
that
ate',
'the
malt
that
lay
in','the
malt
that
lay
in',
'the
house
that
Jack
built','the
house
that
Jack
built']
Slide 307
Slide 307 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
def
parts(number)
data.last(number)
end
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
Slide 308
Slide 308 text
Jan 2015
@sandimetz
Slide 309
Slide 309 text
Jan 2015
@sandimetz
puts
EchoHouse.new.line(1)
'This
is
the
house
that
Jack
built
the
house
that
Jack
built.'
Slide 310
Slide 310 text
Jan 2015
@sandimetz
puts
EchoHouse.new.line(1)
'This
is
the
house
that
Jack
built
the
house
that
Jack
built.'
puts
EchoHouse.new.line(2)
'This
is
the
malt
that
lay
in
the
malt
that
lay
in
the
house
that
Jack
built
the
house
that
Jack
built.'
Slide 311
Slide 311 text
Jan 2015
@sandimetz
puts
EchoHouse.new.line(1)
'This
is
the
house
that
Jack
built
the
house
that
Jack
built.'
puts
EchoHouse.new.line(2)
'This
is
the
malt
that
lay
in
the
malt
that
lay
in
the
house
that
Jack
built
the
house
that
Jack
built.'
puts
EchoHouse.new.line(3)
'This
is
the
rat
that
ate
the
rat
that
ate
the
malt
that
lay
in
the
malt
that
lay
in
the
house
that
Jack
built
the
house
that
Jack
built.'
Slide 312
Slide 312 text
Jan 2015
@sandimetz
puts
EchoHouse.new.line(1)
'This
is
the
house
that
Jack
built
the
house
that
Jack
built.'
puts
EchoHouse.new.line(2)
'This
is
the
malt
that
lay
in
the
malt
that
lay
in
the
house
that
Jack
built
the
house
that
Jack
built.'
puts
EchoHouse.new.line(3)
'This
is
the
rat
that
ate
the
rat
that
ate
the
malt
that
lay
in
the
malt
that
lay
in
the
house
that
Jack
built
the
house
that
Jack
built.'
puts
EchoHouse.new.line(12)
'This
is
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
farmer
sowing
his
corn
that
kept
the
farmer
sowing
his
corn
that
kept
the
rooster
that
crowed
in
the
morn
that
woke
the
rooster
that
crowed
in
the
morn
that
woke
the
priest
all
shaven
and
shorn
that
married
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
man
all
tattered
and
torn
that
kissed
the
maiden
all
forlorn
that
milked
the
maiden
all
forlorn
that
milked
the
cow
with
the
crumpled
horn
that
tossed
the
cow
with
the
crumpled
horn
that
tossed
the
dog
that
worried
the
dog
that
worried
the
cat
that
killed
the
cat
that
killed
the
rat
that
ate
the
rat
that
ate
the
malt
that
lay
in
the
malt
that
lay
in
the
house
that
Jack
built
the
house
that
Jack
built.'
Slide 313
Slide 313 text
Jan 2015
@sandimetz
class
House
def
recite
def
line(number)
def
phrase(number)
def
parts(number)
def
data
end
Slide 314
Slide 314 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
House
def
recite
def
line(number)
def
phrase(number)
def
parts(number)
def
data
end
Slide 315
Slide 315 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
House
def
recite
def
line(number)
def
phrase(number)
def
parts(number)
def
data
end
Slide 316
Slide 316 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
class
House
def
recite
def
line(number)
def
phrase(number)
def
parts(number)
def
data
end
Slide 317
Slide 317 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
class
House
def
recite
def
line(number)
def
phrase(number)
def
parts(number)
def
data
end
Slide 318
Slide 318 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
class
House
def
recite
def
line(number)
def
phrase(number)
def
parts(number)
def
data
end
What could possibly go wrong?
Slide 319
Slide 319 text
Jan 2015
@sandimetz
Slide 320
Slide 320 text
Jan 2015
@sandimetz
New Feature Request:
Slide 321
Slide 321 text
Jan 2015
@sandimetz
New Feature Request:
RandomEchoHouse
Slide 322
Slide 322 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
class
House
def
recite
def
line(number)
def
phrase(number)
def
parts(number)
def
data
end
Slide 323
Slide 323 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
Slide 324
Slide 324 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
Slide 325
Slide 325 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
Duplicate some of the code?
Slide 326
Slide 326 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
RandomEchoHouse
<
RandomHouse <
EchoHouse
data
parts
Slide 327
Slide 327 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
RandomEchoHouse
<
RandomHouse
def
parts(number)
super.zip(super).flatten
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
RandomEchoHouse
<
RandomHouse <
EchoHouse
data
parts
Slide 328
Slide 328 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
RandomEchoHouse
<
RandomHouse
def
parts(number)
super.zip(super).flatten
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
RandomEchoHouse
<
RandomHouse <
EchoHouse
data
parts
Slide 329
Slide 329 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
RandomEchoHouse
<
RandomHouse
def
parts(number)
super.zip(super).flatten
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
RandomEchoHouse
<
RandomHouse <
EchoHouse
Inherit data
parts
Slide 330
Slide 330 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
RandomEchoHouse
<
RandomHouse
def
parts(number)
super.zip(super).flatten
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
RandomEchoHouse
<
RandomHouse <
EchoHouse
Inherit data
Duplicate parts
Slide 331
Slide 331 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
RandomEchoHouse
<
RandomHouse <
EchoHouse
Inherit data
Duplicate parts
Slide 332
Slide 332 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
class
RandomEchoHouse
<
EchoHouse
def
data
@data
||=
super.shuffle
end
end
RandomEchoHouse
<
RandomHouse <
EchoHouse
Inherit data
Duplicate parts
Slide 333
Slide 333 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
class
RandomEchoHouse
<
EchoHouse
def
data
@data
||=
super.shuffle
end
end
RandomEchoHouse
<
RandomHouse <
EchoHouse
Inherit data
Duplicate parts
Slide 334
Slide 334 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
class
RandomEchoHouse
<
EchoHouse
def
data
@data
||=
super.shuffle
end
end
RandomEchoHouse
<
RandomHouse <
EchoHouse
Inherit data
Duplicate parts Inherit
Slide 335
Slide 335 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
class
RandomEchoHouse
<
EchoHouse
def
data
@data
||=
super.shuffle
end
end
RandomEchoHouse
<
RandomHouse <
EchoHouse
Inherit data Duplicate
Duplicate parts Inherit
Slide 336
Slide 336 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
class
EchoHouse
<
House
Slide 337
Slide 337 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
class
EchoHouse
<
House
Duplicate all of the code!
Slide 338
Slide 338 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
class
EchoHouse
<
House
class
RandomEchoHouse
<
House
Slide 339
Slide 339 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
class
EchoHouse
<
House
class
RandomEchoHouse
<
House
Slide 340
Slide 340 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
class
RandomEchoHouse
<
House
def
data
@data
||=
super.shuffle
end
def
parts(number)
super.zip(super).flatten
end
end
Slide 341
Slide 341 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
class
RandomEchoHouse
<
House
def
data
@data
||=
super.shuffle
end
def
parts(number)
super.zip(super).flatten
end
end
Slide 342
Slide 342 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
class
RandomEchoHouse
<
House
def
data
@data
||=
super.shuffle
end
def
parts(number)
super.zip(super).flatten
end
end
Slide 343
Slide 343 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
class
RandomEchoHouse
<
House
def
data
@data
||=
super.shuffle
end
def
parts(number)
super.zip(super).flatten
end
end
Slide 344
Slide 344 text
Jan 2015
@sandimetz
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
class
EchoHouse
<
House
def
parts(number)
super.zip(super).flatten
end
end
class
RandomEchoHouse
<
House
def
data
@data
||=
super.shuffle
end
def
parts(number)
super.zip(super).flatten
end
end
Slide 345
Slide 345 text
Jan 2015
@sandimetz
House
Slide 346
Slide 346 text
Jan 2015
@sandimetz
House
Random
House
Echo
House
Slide 347
Slide 347 text
Jan 2015
@sandimetz
House
Echo
House
Random
House
Slide 348
Slide 348 text
Jan 2015
@sandimetz
House
Echo
House
Random
House
Slide 349
Slide 349 text
Jan 2015
@sandimetz
House
Echo
House
Random
House
Random
House
Slide 350
Slide 350 text
Jan 2015
@sandimetz
House
Echo
House
Random
House
Random
House
Slide 351
Slide 351 text
Jan 2015
@sandimetz
House
Echo
House
Random
House
Random
House
Slide 352
Slide 352 text
Jan 2015
@sandimetz
House
Echo
House
Random
House
Random
House
Echo
House
Slide 353
Slide 353 text
Jan 2015
@sandimetz
House
Echo
House
Random
House
Random
House
Echo
House
Slide 354
Slide 354 text
Jan 2015
@sandimetz
Echo
House
Random
House
Random
House
Echo
House
Slide 355
Slide 355 text
Jan 2015
@sandimetz
Random
House
Echo
House
Slide 356
Slide 356 text
Jan 2015
@sandimetz
Random
House
Echo
House
Slide 357
Slide 357 text
Jan 2015
@sandimetz
Random
House
Echo
House
RandomEcho
House
Slide 358
Slide 358 text
Jan 2015
@sandimetz
Random
House
Echo
House
RandomEcho
House
Slide 359
Slide 359 text
Jan 2015
@sandimetz
Random
House
Echo
House
RandomEcho
House
Slide 360
Slide 360 text
Jan 2015
@sandimetz
Random
House
Echo
House
RandomEcho
House
Slide 361
Slide 361 text
Jan 2015
@sandimetz
Random
House
Echo
House
RandomEcho
House
Slide 362
Slide 362 text
Jan 2015
@sandimetz
Random
House
Echo
House
RandomEcho
House
Slide 363
Slide 363 text
Jan 2015
@sandimetz
Random
House
Echo
House
RandomEcho
House
Slide 364
Slide 364 text
Jan 2015
@sandimetz
Random
House
Echo
House
RandomEcho
House
Slide 365
Slide 365 text
Jan 2015
@sandimetz
Random
House
Echo
House
Slide 366
Slide 366 text
Jan 2015
@sandimetz
Random
House
Echo
House
Slide 367
Slide 367 text
Jan 2015
@sandimetz
Random
House
Echo
House
Slide 368
Slide 368 text
Jan 2015
@sandimetz
Slide 369
Slide 369 text
Jan 2015
@sandimetz
Inheritance
Slide 370
Slide 370 text
Jan 2015
@sandimetz
Inheritance
is for specialization
Slide 371
Slide 371 text
Jan 2015
@sandimetz
Inheritance
is for specialization
is not for sharing code
Slide 372
Slide 372 text
Jan 2015
@sandimetz
RandomHouse is-a House?
Slide 373
Slide 373 text
Jan 2015
@sandimetz
class
House
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
'the
farmer
sowing
his
corn
that
kept',
'the
rooster
that
crowed
in
the
morn
that
woke',
'the
priest
all
shaven
and
shorn
that
married',
'the
man
all
tattered
and
torn
that
kissed',
'the
maiden
all
forlorn
that
milked',
'the
cow
with
the
crumpled
horn
that
tossed',
'the
dog
that
worried',
'the
cat
that
killed',
'the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
Slide 374
Slide 374 text
Jan 2015
@sandimetz
class
House
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
'the
farmer
sowing
his
corn
that
kept',
'the
rooster
that
crowed
in
the
morn
that
woke',
'the
priest
all
shaven
and
shorn
that
married',
'the
man
all
tattered
and
torn
that
kissed',
'the
maiden
all
forlorn
that
milked',
'the
cow
with
the
crumpled
horn
that
tossed',
'the
dog
that
worried',
'the
cat
that
killed',
'the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
What does RandomHouse change?
Slide 375
Slide 375 text
Jan 2015
@sandimetz
Reveal how things differ
by making them more alike
Slide 376
Slide 376 text
Jan 2015
@sandimetz
class
House
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
'the
farmer
sowing
his
corn
that
kept',
'the
rooster
that
crowed
in
the
morn
that
woke',
'the
priest
all
shaven
and
shorn
that
married',
'the
man
all
tattered
and
torn
that
kissed',
'the
maiden
all
forlorn
that
milked',
'the
cow
with
the
crumpled
horn
that
tossed',
'the
dog
that
worried',
'the
cat
that
killed',
'the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
Slide 377
Slide 377 text
Jan 2015
@sandimetz
class
House
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
'the
farmer
sowing
his
corn
that
kept',
'the
rooster
that
crowed
in
the
morn
that
woke',
'the
priest
all
shaven
and
shorn
that
married',
'the
man
all
tattered
and
torn
that
kissed',
'the
maiden
all
forlorn
that
milked',
'the
cow
with
the
crumpled
horn
that
tossed',
'the
dog
that
worried',
'the
cat
that
killed',
'the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
Make this
Slide 378
Slide 378 text
Jan 2015
@sandimetz
class
House
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
'the
farmer
sowing
his
corn
that
kept',
'the
rooster
that
crowed
in
the
morn
that
woke',
'the
priest
all
shaven
and
shorn
that
married',
'the
man
all
tattered
and
torn
that
kissed',
'the
maiden
all
forlorn
that
milked',
'the
cow
with
the
crumpled
horn
that
tossed',
'the
dog
that
worried',
'the
cat
that
killed',
'the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
Make this
More like this
Slide 379
Slide 379 text
Jan 2015
@sandimetz
class
House
def
data
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
'the
farmer
sowing
his
corn
that
kept',
'the
rooster
that
crowed
in
the
morn
that
woke',
'the
priest
all
shaven
and
shorn
that
married',
'the
man
all
tattered
and
torn
that
kissed',
'the
maiden
all
forlorn
that
milked',
'the
cow
with
the
crumpled
horn
that
tossed',
'the
dog
that
worried',
'the
cat
that
killed',
'the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
end
Slide 380
Slide 380 text
Jan 2015
@sandimetz
class
House
DATA
=
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
'the
farmer
sowing
his
corn
that
kept',
'the
rooster
that
crowed
in
the
morn
that
woke',
'the
priest
all
shaven
and
shorn
that
married',
'the
man
all
tattered
and
torn
that
kissed',
'the
maiden
all
forlorn
that
milked',
'the
cow
with
the
crumpled
horn
that
tossed',
'the
dog
that
worried',
'the
cat
that
killed',
'the
rat
that
ate',
'the
malt
that
lay
in',
'the
house
that
Jack
built']
end
Slide 381
Slide 381 text
Jan 2015
@sandimetz
class
House
DATA
=
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
house
that
Jack
built']
end
Slide 382
Slide 382 text
Jan 2015
@sandimetz
class
House
DATA
=
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
house
that
Jack
built']
def
data
DATA
end
end
Slide 383
Slide 383 text
Jan 2015
@sandimetz
class
House
DATA
=
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
house
that
Jack
built']
def
data
DATA
end
end
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
Slide 384
Slide 384 text
Jan 2015
@sandimetz
class
House
DATA
=
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
house
that
Jack
built']
def
data
@data
||=
DATA
end
end
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
Slide 385
Slide 385 text
Jan 2015
@sandimetz
class
House
DATA
=
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
house
that
Jack
built']
def
data
@data
||=
DATA
end
end
class
RandomHouse
<
House
def
data
@data
||=
DATA.shuffle
end
end
Slide 386
Slide 386 text
Jan 2015
@sandimetz
class
House
DATA
=
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
house
that
Jack
built']
def
data
@data
||=
DATA
end
end
class
RandomHouse
<
House
def
data
@data
||=
DATA.shuffle
end
end
What changed?
Slide 387
Slide 387 text
Jan 2015
@sandimetz
Name the concept
Slide 388
Slide 388 text
Jan 2015
@sandimetz
House
RandomHouse
Slide 389
Slide 389 text
Jan 2015
@sandimetz
House DATA
RandomHouse DATA
Slide 390
Slide 390 text
Jan 2015
@sandimetz
House DATA
RandomHouse DATA shuffle
Slide 391
Slide 391 text
Jan 2015
@sandimetz
class
House DATA
RandomHouse DATA shuffle
Slide 392
Slide 392 text
Jan 2015
@sandimetz
class data
House DATA
RandomHouse DATA shuffle
Slide 393
Slide 393 text
Jan 2015
@sandimetz
class data ?????
House DATA
RandomHouse DATA shuffle
Slide 394
Slide 394 text
Jan 2015
@sandimetz
class data random??
House DATA
RandomHouse DATA shuffle
Slide 395
Slide 395 text
Jan 2015
@sandimetz
class data order!
House DATA
RandomHouse DATA shuffle
Slide 396
Slide 396 text
Jan 2015
@sandimetz
class data order
House DATA
RandomHouse DATA shuffle
Slide 397
Slide 397 text
Jan 2015
@sandimetz
class data order
House DATA
RandomHouse DATA shuffle
This is not nothing
Slide 398
Slide 398 text
Jan 2015
@sandimetz
class data order
House DATA
RandomHouse DATA shuffle
It's an order algorithm
Slide 399
Slide 399 text
Jan 2015
@sandimetz
class data order
House DATA
RandomHouse DATA shuffle
It's an order algorithm
just as valid as this one
Slide 400
Slide 400 text
Jan 2015
@sandimetz
Order is-a House?
Slide 401
Slide 401 text
Jan 2015
@sandimetz
Orderer is a role
Slide 402
Slide 402 text
Jan 2015
@sandimetz
class
RandomOrder
def
order(data)
data.shuffle
end
end
Slide 403
Slide 403 text
Jan 2015
@sandimetz
class
DefaultOrder
end
class
RandomOrder
def
order(data)
data.shuffle
end
end
Slide 404
Slide 404 text
Jan 2015
@sandimetz
class
DefaultOrder
def
order(data)
end
end
class
RandomOrder
def
order(data)
data.shuffle
end
end
Slide 405
Slide 405 text
Jan 2015
@sandimetz
class
DefaultOrder
def
order(data)
data
end
end
class
RandomOrder
def
order(data)
data.shuffle
end
end
Slide 406
Slide 406 text
Jan 2015
@sandimetz
class
House
DATA
=
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
house
that
Jack
built']
def
data
DATA
end
end
class
RandomHouse
<
House
def
data
@data
||=
super.shuffle
end
end
Slide 407
Slide 407 text
Jan 2015
@sandimetz
class
House
DATA
=
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
house
that
Jack
built']
def
data
DATA
end
end
Slide 408
Slide 408 text
Jan 2015
@sandimetz
class
House
DATA
=
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
house
that
Jack
built']
def
data
DATA
end
#
...
end
Slide 409
Slide 409 text
Jan 2015
@sandimetz
class
House
DATA
=
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
house
that
Jack
built']
attr_reader
:data
def
data
DATA
end
#
...
end
Slide 410
Slide 410 text
Jan 2015
@sandimetz
class
House
DATA
=
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
house
that
Jack
built']
attr_reader
:data
def
initialize
@data
=
DATA
end
def
data
DATA
end
#
...
end
Slide 411
Slide 411 text
Jan 2015
@sandimetz
class
House
DATA
=
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
house
that
Jack
built']
attr_reader
:data
def
initialize
@data
=
DATA
end
#
...
end
Slide 412
Slide 412 text
Jan 2015
@sandimetz
class
House
DATA
=
[
'the
horse
and
the
hound
and
the
horn
that
belonged
to',
#
...
'the
house
that
Jack
built']
attr_reader
:data
def
initialize
@data
=
DATA
end
#
...
end
Slide 413
Slide 413 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize
@data
=
DATA
end
#
...
end
Slide 414
Slide 414 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize
@data
=
DATA
end
#
...
end
Slide 415
Slide 415 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize
@data
=
DATA
end
#
...
end
Remove 'ordering' responsibility from House
Slide 416
Slide 416 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize
@data
=
DATA
end
#
...
end
class
DefaultOrder
def
order(data)
data
end
end
Slide 417
Slide 417 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new)
@data
=
DATA
end
#
...
end
class
DefaultOrder
def
order(data)
data
end
end
Slide 418
Slide 418 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new)
@data
=
DATA
end
#
...
end
class
DefaultOrder
def
order(data)
data
end
end
Slide 419
Slide 419 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new)
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultOrder
def
order(data)
data
end
end
Slide 420
Slide 420 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new)
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultOrder
def
order(data)
data
end
end
puts
House.new.line(12)
Slide 421
Slide 421 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new)
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultOrder
def
order(data)
data
end
end
puts
House.new.line(12)
=>
'This
is
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
farmer
sowing
his
corn
that
kept
the
rooster
that
crowed
in
the
morn
that
woke
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
maiden
all
forlorn
that
milked
the
cow
with
the
crumpled
horn
that
tossed
the
dog
that
worried
the
cat
that
killed
the
rat
that
ate
the
malt
that
lay
in
the
house
that
Jack
built.'
Slide 422
Slide 422 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new)
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultOrder
def
order(data)
data
end
end
puts
House.new.line(12)
=>
'This
is
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
farmer
sowing
his
corn
that
kept
the
rooster
that
crowed
in
the
morn
that
woke
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
maiden
all
forlorn
that
milked
the
cow
with
the
crumpled
horn
that
tossed
the
dog
that
worried
the
cat
that
killed
the
rat
that
ate
the
malt
that
lay
in
the
house
that
Jack
built.'
Slide 423
Slide 423 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new)
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultOrder
def
order(data)
data
end
end
puts
House.new.line(12)
=>
'This
is
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
farmer
sowing
his
corn
that
kept
the
rooster
that
crowed
in
the
morn
that
woke
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
maiden
all
forlorn
that
milked
the
cow
with
the
crumpled
horn
that
tossed
the
dog
that
worried
the
cat
that
killed
the
rat
that
ate
the
malt
that
lay
in
the
house
that
Jack
built.'
More code
Slide 424
Slide 424 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new)
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultOrder
def
order(data)
data
end
end
puts
House.new.line(12)
=>
'This
is
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
farmer
sowing
his
corn
that
kept
the
rooster
that
crowed
in
the
morn
that
woke
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
maiden
all
forlorn
that
milked
the
cow
with
the
crumpled
horn
that
tossed
the
dog
that
worried
the
cat
that
killed
the
rat
that
ate
the
malt
that
lay
in
the
house
that
Jack
built.'
More code
Same behavior
Slide 425
Slide 425 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new)
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultOrder
def
order(data)
data
end
end
puts
House.new.line(12)
=>
'This
is
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
farmer
sowing
his
corn
that
kept
the
rooster
that
crowed
in
the
morn
that
woke
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
maiden
all
forlorn
that
milked
the
cow
with
the
crumpled
horn
that
tossed
the
dog
that
worried
the
cat
that
killed
the
rat
that
ate
the
malt
that
lay
in
the
house
that
Jack
built.'
More code
Same behavior
Awesome
Slide 426
Slide 426 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new)
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultOrder
def
order(data)
data
end
end
puts
House.new.line(12)
=>
'This
is
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
farmer
sowing
his
corn
that
kept
the
rooster
that
crowed
in
the
morn
that
woke
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
maiden
all
forlorn
that
milked
the
cow
with
the
crumpled
horn
that
tossed
the
dog
that
worried
the
cat
that
killed
the
rat
that
ate
the
malt
that
lay
in
the
house
that
Jack
built.'
Slide 427
Slide 427 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new)
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultOrder
def
order(data)
data
end
end
puts
House.new.line(12)
class
RandomOrder
def
order(data)
data.shuffle
end
end
Slide 428
Slide 428 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new)
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultOrder
def
order(data)
data
end
end
puts
House.new(
).line(12)
class
RandomOrder
def
order(data)
data.shuffle
end
end
Slide 429
Slide 429 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new)
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultOrder
def
order(data)
data
end
end
puts
House.new(orderer:
RandomOrder.new).line(12)
class
RandomOrder
def
order(data)
data.shuffle
end
end
Slide 430
Slide 430 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new)
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultOrder
def
order(data)
data
end
end
puts
House.new(orderer:
RandomOrder.new).line(12)
=>
'This
is
the
rooster
that
crowed
in
the
morn
that
woke
the
farmer
sowing
his
corn
that
kept
the
dog
that
worried
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
malt
that
lay
in
the
cow
with
the
crumpled
horn
that
tossed
the
house
that
Jack
built
the
cat
that
killed
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
class
RandomOrder
def
order(data)
data.shuffle
end
end
Slide 431
Slide 431 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new)
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultOrder
def
order(data)
data
end
end
puts
House.new(orderer:
RandomOrder.new).line(12)
=>
'This
is
the
rooster
that
crowed
in
the
morn
that
woke
the
farmer
sowing
his
corn
that
kept
the
dog
that
worried
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
malt
that
lay
in
the
cow
with
the
crumpled
horn
that
tossed
the
house
that
Jack
built
the
cat
that
killed
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
class
RandomOrder
def
order(data)
data.shuffle
end
end
Slide 432
Slide 432 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new)
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultOrder
def
order(data)
data
end
end
puts
House.new(orderer:
RandomOrder.new).line(12)
=>
'This
is
the
rooster
that
crowed
in
the
morn
that
woke
the
farmer
sowing
his
corn
that
kept
the
dog
that
worried
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
malt
that
lay
in
the
cow
with
the
crumpled
horn
that
tossed
the
house
that
Jack
built
the
cat
that
killed
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
class
RandomOrder
def
order(data)
data.shuffle
end
end
Slide 433
Slide 433 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new)
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultOrder
def
order(data)
data
end
end
puts
House.new(orderer:
RandomOrder.new).line(12)
=>
'This
is
the
rooster
that
crowed
in
the
morn
that
woke
the
farmer
sowing
his
corn
that
kept
the
dog
that
worried
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
malt
that
lay
in
the
cow
with
the
crumpled
horn
that
tossed
the
house
that
Jack
built
the
cat
that
killed
the
maiden
all
forlorn
that
milked
the
rat
that
ate.'
class
RandomOrder
def
order(data)
data.shuffle
end
end
Slide 434
Slide 434 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new)
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultOrder
def
order(data)
data
end
end
puts
House.new(orderer:
RandomOrder.new).line(12)
=>
'This
is
the
rooster
that
crowed
in
the
morn
that
woke
the
cat
that
killed
the
cow
with
the
crumpled
horn
that
tossed
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
farmer
sowing
his
corn
that
kept
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
house
that
Jack
built
the
malt
that
lay
in
the
rat
that
ate
the
maiden
all
forlorn
that
milked
the
dog
that
worried.'
class
RandomOrder
def
order(data)
data.shuffle
end
end
Composition
Slide 435
Slide 435 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new)
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultOrder
def
order(data)
data
end
end
puts
House.new(orderer:
RandomOrder.new).line(12)
=>
'This
is
the
rooster
that
crowed
in
the
morn
that
woke
the
cat
that
killed
the
cow
with
the
crumpled
horn
that
tossed
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
farmer
sowing
his
corn
that
kept
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
house
that
Jack
built
the
malt
that
lay
in
the
rat
that
ate
the
maiden
all
forlorn
that
milked
the
dog
that
worried.'
class
RandomOrder
def
order(data)
data.shuffle
end
end
Inject an object
to play the role
of the thing that varies
Slide 436
Slide 436 text
Jan 2015
@sandimetz
Echo?
Slide 437
Slide 437 text
Jan 2015
@sandimetz
class
EchoFormatter
def
format(parts)
parts.zip(parts).flatten
end
end
Slide 438
Slide 438 text
Jan 2015
@sandimetz
class
DefaultFormatter
def
format(parts)
parts
end
end
class
EchoFormatter
def
format(parts)
parts.zip(parts).flatten
end
end
Slide 439
Slide 439 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new)
@data
=
orderer.order(DATA)
end
#
...
end
Slide 440
Slide 440 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new)
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultFormatter
def
format(parts)
parts
end
end
Slide 441
Slide 441 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new,
formatter:
DefaultFormatter.new)
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultFormatter
def
format(parts)
parts
end
end
Slide 442
Slide 442 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new,
formatter:
DefaultFormatter.new)
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultFormatter
def
format(parts)
parts
end
end
Slide 443
Slide 443 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new,
formatter:
DefaultFormatter.new)
@formatter
=
formatter
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultFormatter
def
format(parts)
parts
end
end
Slide 444
Slide 444 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new,
formatter:
DefaultFormatter.new)
@formatter
=
formatter
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultFormatter
def
format(parts)
parts
end
end
Slide 445
Slide 445 text
Jan 2015
@sandimetz
class
House
attr_reader
:data
def
initialize(orderer:
DefaultOrder.new,
formatter:
DefaultFormatter.new)
@formatter
=
formatter
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultFormatter
def
format(parts)
parts
end
end
Slide 446
Slide 446 text
Jan 2015
@sandimetz
class
House
attr_reader
:formatter,
:data
def
initialize(orderer:
DefaultOrder.new,
formatter:
DefaultFormatter.new)
@formatter
=
formatter
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultFormatter
def
format(parts)
parts
end
end
Slide 447
Slide 447 text
Jan 2015
@sandimetz
class
House
attr_reader
:formatter,
:data
def
initialize(orderer:
DefaultOrder.new,
formatter:
DefaultFormatter.new)
@formatter
=
formatter
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultFormatter
def
format(parts)
parts
end
end
Slide 448
Slide 448 text
Jan 2015
@sandimetz
class
House
attr_reader
:formatter,
:data
def
initialize(orderer:
DefaultOrder.new,
formatter:
DefaultFormatter.new)
@formatter
=
formatter
@data
=
orderer.order(DATA)
end
def
parts(number)
data.last(number)
end
#
...
end
class
DefaultFormatter
def
format(parts)
parts
end
end
Slide 449
Slide 449 text
Jan 2015
@sandimetz
class
House
attr_reader
:formatter,
:data
def
initialize(orderer:
DefaultOrder.new,
formatter:
DefaultFormatter.new)
@formatter
=
formatter
@data
=
orderer.order(DATA)
end
def
parts(number)
data.last(number)
end
#
...
end
class
DefaultFormatter
def
format(parts)
parts
end
end
Slide 450
Slide 450 text
Jan 2015
@sandimetz
class
House
attr_reader
:formatter,
:data
def
initialize(orderer:
DefaultOrder.new,
formatter:
DefaultFormatter.new)
@formatter
=
formatter
@data
=
orderer.order(DATA)
end
def
parts(number)
formatter.format(data.last(number))
end
#
...
end
class
DefaultFormatter
def
format(parts)
parts
end
end
Slide 451
Slide 451 text
Jan 2015
@sandimetz
class
House
attr_reader
:formatter,
:data
def
initialize(orderer:
DefaultOrder.new,
formatter:
DefaultFormatter.new)
@formatter
=
formatter
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultFormatter
def
format(parts)
parts
end
end
Slide 452
Slide 452 text
Jan 2015
@sandimetz
class
House
attr_reader
:formatter,
:data
def
initialize(orderer:
DefaultOrder.new,
formatter:
DefaultFormatter.new)
@formatter
=
formatter
@data
=
orderer.order(DATA)
end
#
...
end
class
DefaultFormatter
def
format(parts)
parts
end
end
Slide 453
Slide 453 text
Jan 2015
@sandimetz
class
House
attr_reader
:formatter,
:data
def
initialize(orderer:
DefaultOrder.new,
formatter:
DefaultFormatter.new)
@formatter
=
formatter
@data
=
orderer.order(DATA)
end
#
...
end
puts
House.new.line(12)
class
DefaultFormatter
def
format(parts)
parts
end
end
Slide 454
Slide 454 text
Jan 2015
@sandimetz
class
House
attr_reader
:formatter,
:data
def
initialize(orderer:
DefaultOrder.new,
formatter:
DefaultFormatter.new)
@formatter
=
formatter
@data
=
orderer.order(DATA)
end
#
...
end
puts
House.new.line(12)
=>
'This
is
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
farmer
sowing
his
corn
that
kept
the
rooster
that
crowed
in
the
morn
that
woke
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
maiden
all
forlorn
that
milked
the
cow
with
the
crumpled
horn
that
tossed
the
dog
that
worried
the
cat
that
killed
the
rat
that
ate
the
malt
that
lay
in
the
house
that
Jack
built.'
class
DefaultFormatter
def
format(parts)
parts
end
end
Slide 455
Slide 455 text
Jan 2015
@sandimetz
class
DefaultFormatter
def
format(parts)
parts
end
end
class
House
attr_reader
:formatter,
:data
def
initialize(orderer:
DefaultOrder.new,
formatter:
DefaultFormatter.new)
@formatter
=
formatter
@data
=
orderer.order(DATA)
end
#
...
end
class
EchoFormatter
def
format(parts)
parts.zip(parts).flatten
end
end
Slide 456
Slide 456 text
Jan 2015
@sandimetz
class
DefaultFormatter
def
format(parts)
parts
end
end
class
House
attr_reader
:formatter,
:data
def
initialize(orderer:
DefaultOrder.new,
formatter:
DefaultFormatter.new)
@formatter
=
formatter
@data
=
orderer.order(DATA)
end
#
...
end
puts
House.new(formatter:
EchoFormatter.new).line(12)
class
EchoFormatter
def
format(parts)
parts.zip(parts).flatten
end
end
Slide 457
Slide 457 text
Jan 2015
@sandimetz
class
DefaultFormatter
def
format(parts)
parts
end
end
class
House
attr_reader
:formatter,
:data
def
initialize(orderer:
DefaultOrder.new,
formatter:
DefaultFormatter.new)
@formatter
=
formatter
@data
=
orderer.order(DATA)
end
#
...
end
puts
House.new(formatter:
EchoFormatter.new).line(12)
=>
'This
is
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
horse
and
the
hound
and
the
horn
that
belonged
to
the
farmer
sowing
his
corn
that
kept
the
farmer
sowing
his
corn
that
kept
the
rooster
that
crowed
in
the
morn
that
woke
the
rooster
that
crowed
in
the
morn
that
woke
the
priest
all
shaven
and
shorn
that
married
the
priest
all
shaven
and
shorn
that
married
the
man
all
tattered
and
torn
that
kissed
the
man
class
EchoFormatter
def
format(parts)
parts.zip(parts).flatten
end
end
Slide 458
Slide 458 text
Jan 2015
@sandimetz
class
DefaultOrder
def
order(data)
data
end
end
class
RandomOrder
def
order(data)
data.shuffle
end
end
Orderer Role
Slide 459
Slide 459 text
Jan 2015
@sandimetz
class
DefaultFormatter
def
format(parts)
parts
end
end
class
EchoFormatter
def
format(parts)
parts.zip(parts).flatten
end
end
class
DefaultOrder
def
order(data)
data
end
end
class
RandomOrder
def
order(data)
data.shuffle
end
end
Orderer Role Formatter Role
Slide 460
Slide 460 text
Jan 2015
@sandimetz
puts
House.new.line(12)
Slide 461
Slide 461 text
Jan 2015
@sandimetz
Slide 462
Slide 462 text
Jan 2015
@sandimetz
puts
House.new.recite
Slide 463
Slide 463 text
Jan 2015
@sandimetz
puts
House.new.recite
puts
House.new(orderer:
RandomOrder.new).recite
Slide 464
Slide 464 text
Jan 2015
@sandimetz
puts
House.new.recite
puts
House.new(orderer:
RandomOrder.new).recite
puts
House.new(formatter:
EchoFormatter.new).recite
Slide 465
Slide 465 text
Jan 2015
@sandimetz
puts
House.new.recite
puts
House.new(orderer:
RandomOrder.new).recite
puts
House.new(formatter:
EchoFormatter.new).recite
puts
House.new(orderer:
RandomOrder.new,
formatter:
EchoFormatter.new).recite
Slide 466
Slide 466 text
Jan 2015
@sandimetz
puts
House.new.recite
puts
House.new(orderer:
RandomOrder.new).recite
puts
House.new(formatter:
EchoFormatter.new).recite
puts
House.new(orderer:
RandomOrder.new,
formatter:
EchoFormatter.new).recite
More code?
Slide 467
Slide 467 text
Jan 2015
@sandimetz
puts
House.new.recite
puts
House.new(orderer:
RandomOrder.new).recite
puts
House.new(formatter:
EchoFormatter.new).recite
puts
House.new(orderer:
RandomOrder.new,
formatter:
EchoFormatter.new).recite
Slide 468
Slide 468 text
Jan 2015
@sandimetz
puts
House.new.recite
puts
House.new(orderer:
RandomOrder.new).recite
puts
House.new(formatter:
EchoFormatter.new).recite
puts
House.new(orderer:
RandomOrder.new,
formatter:
EchoFormatter.new).recite
Less code!
Slide 469
Slide 469 text
Jan 2015
@sandimetz
puts
House.new.recite
puts
House.new(orderer:
RandomOrder.new).recite
puts
House.new(formatter:
EchoFormatter.new).recite
puts
House.new(orderer:
RandomOrder.new,
formatter:
EchoFormatter.new).recite
Less code!
No duplication
Slide 470
Slide 470 text
Jan 2015
@sandimetz
puts
House.new.recite
puts
House.new(orderer:
RandomOrder.new).recite
puts
House.new(formatter:
EchoFormatter.new).recite
puts
House.new(orderer:
RandomOrder.new,
formatter:
EchoFormatter.new).recite
Less code!
Pluggable behavior
Slide 471
Slide 471 text
Jan 2015
@sandimetz
House
Echo
House
Random
House
Slide 472
Slide 472 text
Jan 2015
@sandimetz
House
Slide 473
Slide 473 text
Jan 2015
@sandimetz
House
Slide 474
Slide 474 text
Jan 2015
@sandimetz
House
1) Isolate the thing that varies
Slide 475
Slide 475 text
Jan 2015
@sandimetz
House
1) Isolate the thing that varies
Slide 476
Slide 476 text
Jan 2015
@sandimetz
House
1) Isolate the thing that varies
Slide 477
Slide 477 text
Jan 2015
@sandimetz
House
Slide 478
Slide 478 text
Jan 2015
@sandimetz
House
Slide 479
Slide 479 text
Jan 2015
@sandimetz
House
2) Name the Concept
Slide 480
Slide 480 text
Jan 2015
@sandimetz
House
2) Name the Concept
Slide 481
Slide 481 text
Jan 2015
@sandimetz
House
Order Format
Slide 482
Slide 482 text
Jan 2015
@sandimetz
House
Order Format
3) Define the Role
Slide 483
Slide 483 text
Jan 2015
@sandimetz
House
Order Format
3) Define the Role
Slide 484
Slide 484 text
Jan 2015
@sandimetz
House
Orderer Formatter
Slide 485
Slide 485 text
Jan 2015
@sandimetz
House
Orderer Formatter
4) Inject the player
Slide 486
Slide 486 text
Jan 2015
@sandimetz
House
Orderer Formatter
Slide 487
Slide 487 text
Jan 2015
@sandimetz
House
Orderer Formatter
Slide 488
Slide 488 text
Jan 2015
@sandimetz
puts
House.new.recite
puts
House.new(orderer:
RandomOrder.new).recite
puts
House.new(formatter:
EchoFormatter.new).recite
puts
House.new(orderer:
RandomOrder.new,
formatter:
EchoFormatter.new).recite
Slide 489
Slide 489 text
Jan 2015
@sandimetz
puts
House.new.recite
puts
House.new(orderer:
RandomOrder.new).recite
puts
House.new(formatter:
EchoFormatter.new).recite
puts
House.new(orderer:
RandomOrder.new,
formatter:
EchoFormatter.new).recite
Composition
Slide 490
Slide 490 text
Jan 2015
@sandimetz
puts
House.new.recite
puts
House.new(orderer:
RandomOrder.new).recite
puts
House.new(formatter:
EchoFormatter.new).recite
puts
House.new(orderer:
RandomOrder.new,
formatter:
EchoFormatter.new).recite
Composition
+
Dependency Injection
Slide 491
Slide 491 text
Jan 2015
@sandimetz
puts
House.new.recite
puts
House.new(orderer:
RandomOrder.new).recite
puts
House.new(formatter:
EchoFormatter.new).recite
puts
House.new(orderer:
RandomOrder.new,
formatter:
EchoFormatter.new).recite
Object-Oriented Design
Slide 492
Slide 492 text
Jan 2015
@sandimetz
Smalltalk Infected
Condition Averse
Message Centric
Abstraction Seeking
Slide 493
Slide 493 text
Jan 2015
@sandimetz
Smalltalk Infected
Condition Averse
Message Centric
Abstraction Seeking
Slide 494
Slide 494 text
Jan 2015
@sandimetz
Summary
Slide 495
Slide 495 text
Jan 2015
@sandimetz
Slide 496
Slide 496 text
Jan 2015
@sandimetz
If you're talking to nil
Slide 497
Slide 497 text
Jan 2015
@sandimetz
If you're talking to nil
it's something
Slide 498
Slide 498 text
Jan 2015
@sandimetz
Null Object Pattern
Active Nothing
Slide 499
Slide 499 text
Jan 2015
@sandimetz
Slide 500
Slide 500 text
Jan 2015
@sandimetz
Ware Inheritance
Slide 501
Slide 501 text
Jan 2015
@sandimetz
Ware Inheritance
It is not for sharing behavior
Slide 502
Slide 502 text
Jan 2015
@sandimetz
There's no such thing as
one specialization
Slide 503
Slide 503 text
Jan 2015
@sandimetz
Slide 504
Slide 504 text
Jan 2015
@sandimetz
Isolate the thing that varies
Slide 505
Slide 505 text
Jan 2015
@sandimetz
Isolate the thing that varies
Name the concept
Slide 506
Slide 506 text
Jan 2015
@sandimetz
Isolate the thing that varies
Name the concept
Define the role
Slide 507
Slide 507 text
Jan 2015
@sandimetz
Isolate the thing that varies
Name the concept
Define the role
Inject the players
Slide 508
Slide 508 text
Jan 2015
@sandimetz
Believe in nothing
Slide 509
Slide 509 text
Jan 2015
@sandimetz
Nothing
is always
Something
Slide 510
Slide 510 text
Jan 2015
@sandimetz
Sandi Metz
@sandimetz
http://sandimetz.com
Slide 511
Slide 511 text
Jan 2015
@sandimetz
http://poodr.com
Slide 512
Slide 512 text
Jan 2015
@sandimetz
http://99bottlesbook.com
Practical Programming Book
99 Bottles of OOP
Slide 513
Slide 513 text
Jan 2015
@sandimetz
Next Public Course
POODNYC
Oct 19-21, 2015
New York City
Slide 514
Slide 514 text
Jan 2015
@sandimetz
Stickers?
Slide 515
Slide 515 text
Jan 2015
@sandimetz
Stickers?
Slide 516
Slide 516 text
Jan 2015
@sandimetz
Temporary
Tattoos!
Slide 517
Slide 517 text
Jan 2015
@sandimetz
Thanks
Slide 518
Slide 518 text
Jan 2015
@sandimetz
Sandi Metz
@sandimetz
http://sandimetz.com