Polly Want A Message (DeconstructConf)

May 2018
@sandimetz
Sandi Metz
Polly
want a
Message

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@sandimetz May 2018
Path to Pain

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@sandimetz May 2018
Design Stamina
Hypothesis
- Martin Fowler

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@sandimetz May 2018
#1
Design Stamina
Hypothesis
- Martin Fowler

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@sandimetz May 2018

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@sandimetz May 2018
Over Design

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@sandimetz May 2018

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@sandimetz May 2018
Under Design

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@sandimetz May 2018

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@sandimetz May 2018
???

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@sandimetz May 2018

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@sandimetz May 2018
Ouch

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@sandimetz May 2018
Procedures vs OO
-Me

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@sandimetz May 2018
#2
Procedures vs OO
-Me

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@sandimetz May 2018

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@sandimetz May 2018
Ouch

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@sandimetz May 2018
Churn vs. Complexity
- Michael Feathers

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@sandimetz May 2018
#3
Churn vs. Complexity
- Michael Feathers

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@sandimetz May 2018

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@sandimetz May 2018
Ouch

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@sandimetz May 2018
What matters, suﬀers
-Me

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@sandimetz May 2018
#4
What matters, suﬀers
-Me

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@sandimetz May 2018

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@sandimetz May 2018
GPA 1.8

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@sandimetz May 2018

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@sandimetz May 2018
GPA 2.58

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@sandimetz May 2018

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@sandimetz May 2018
GPA 2.97

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@sandimetz May 2018

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@sandimetz May 2018
#1 Design Stamina Hypothesis

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@sandimetz May 2018
#2 Procedures vs OO

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@sandimetz May 2018
#2 Procedures vs OO
#3 Churn vs Complexity

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@sandimetz May 2018
#2 Procedures vs OO
#3 Churn vs Complexity
#4 What matters, suﬀers

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@sandimetz May 2018
Interlude

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@sandimetz May 2018
Wherein things go
badly wrong
Interlude

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@sandimetz May 2018
File.read("/path/to/filename").split("\n")

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@sandimetz May 2018
Change #1

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@sandimetz May 2018
Change #1
Read from
Git Tag

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@sandimetz May 2018
class GitCmd
attr_accessor :repository, :tagname, :filename
def show
`git #{git_dir} show #{tagname}:#{filename}`
end
private
def git_dir
%Q[--git-dir="#{repository}"]
end
end

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@sandimetz May 2018
if git_cmd
git_cmd.repository = repository
git_cmd.tagname = tag
git_cmd.filename = filename
git_cmd.show.split("\n")
else
File.read(filename).split("\n")
end

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@sandimetz May 2018
def lines
if git_cmd
else
end
end

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@sandimetz May 2018
class Listing
attr_reader :filename, :repository, :tag, :git_cmd
def initialize(filename:, repository: nil, tag: nil, git_cmd: nil)
@filename = filename
@repository = repository
@tag = tag
@git_cmd = git_cmd
end
def lines
if git_cmd
else
end
end
end

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@sandimetz May 2018
Change #2

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@sandimetz May 2018
Change #2
Partial listings

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@sandimetz May 2018
Change #2
Partial listings
"1, 3-4, 15, 37-50"

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@sandimetz May 2018
Easy
is the enemy of
simple

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@sandimetz May 2018
class Listing
@tag = tag
@git_cmd = git_cmd
end
# ...
end

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@sandimetz May 2018
class Listing
def initialize(filename:, repository: nil, tag: nil,
git_cmd: nil)
@tag = tag
@git_cmd = git_cmd
end
# ...
end

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@sandimetz May 2018
class Listing
attr_reader :filename, :line_numbers, :repository, :tag, :git_cmd
def initialize(filename:, line_numbers: nil, repository: nil, tag: nil,
git_cmd: nil)
@tag = tag
@git_cmd = git_cmd
end
# ...
end

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@sandimetz May 2018
class Listing
git_cmd: nil)
@line_numbers = line_numbers
@tag = tag
@git_cmd = git_cmd
end
# ...
end

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@sandimetz May 2018
class Listing
# ...

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@sandimetz May 2018
class Listing
# ...
def lines
if git_cmd
else
end
end

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@sandimetz May 2018
class Listing
# ...
def lines
if git_cmd
else
end
end New Conditional Here

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@sandimetz May 2018
class Listing
# ...
def lines
if git_cmd
else
end
end

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@sandimetz May 2018
class Listing
# ...
def lines
if git_cmd
else
end
end
def git_lines
end

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@sandimetz May 2018
class Listing
# ...
def lines
if git_cmd
git_lines
else
end
end
def git_lines
end

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@sandimetz May 2018
class Listing
# ...
def lines
if git_cmd
git_lines
else
end
end

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@sandimetz May 2018
class Listing
# ...
def lines
if git_cmd
git_lines
else
end
end
def file_lines
end

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@sandimetz May 2018
class Listing
# ...
def lines
if git_cmd
git_lines
else
file_lines
end
end
def file_lines
end

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@sandimetz May 2018
class Listing
# ...
def lines
if git_cmd
git_lines
else
file_lines
end
end

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@sandimetz May 2018
class Listing
# ...
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
end

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@sandimetz May 2018
class Listing
# ...
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
if line_numbers
return lines_to_print(all_lines)
end
all_lines
end

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@sandimetz May 2018
# "1, 3-4, 15, 37-50"
def lines_to_print(all_lines)
specs = line_numbers.gsub(/[‘|’]/, "").gsub(/ /,'').split(",")
specs.collect {|spec|
edges = spec.split('-').collect(&:to_i)
individual_numbers = (edges.min.to_i..edges.max.to_i).to_a
individual_numbers.collect {|i| all_lines[i - 1]}.compact
}.flatten.compact
end

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@sandimetz May 2018
# "1, 3-4, 15, 37-50"
}.flatten.compact
end
Ouch

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@sandimetz May 2018
# "1, 3-4, 15, 37-50"
}.flatten.compact
end

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@sandimetz May 2018
Change #3

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@sandimetz May 2018
Change #3
Dynamic Comments

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@sandimetz May 2018
Change #3
Dynamic Comments
"1, 3-4, 15, 37-50"

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@sandimetz May 2018
Change #3
Dynamic Comments
"1, #4, 3-4, #6, 15, 37-50"

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@sandimetz May 2018
# "1, 3-4, 15, 37-50"
}.flatten.compact
end

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@sandimetz May 2018
# "1, #4, 3-4, #6, 15, 37-50"
}.flatten.compact
end

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@sandimetz May 2018
# "1, #4, 3-4, #6, 15, 37-50"
}.flatten.compact
end New Conditional Here

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@sandimetz May 2018
# "1, #4, 3-4, #6, 15, 37-50"
}.flatten.compact
end

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@sandimetz May 2018
# "1, #4, 3-4, #6, 15, 37-50"
if spec.include?('#')
else
end
}.flatten.compact
end

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@sandimetz May 2018
# "1, #4, 3-4, #6, 15, 37-50"
num_spaces = spec.delete("#").to_i
(" " * num_spaces) + "# ..."
else
end
}.flatten.compact
end

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@sandimetz May 2018
Change #4

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@sandimetz May 2018
Change #4
Left Justiﬁcation

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@sandimetz May 2018
class Listing
git_cmd: nil)
@tag = tag
@git_cmd = git_cmd
end
# ...

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@sandimetz May 2018
class Listing
def initialize(filename:, line_numbers: nil,
repository: nil, tag: nil, git_cmd: nil)
@tag = tag
@git_cmd = git_cmd
end
# ...

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@sandimetz May 2018
class Listing
attr_reader :filename, :line_numbers, :left_just, :repository, :tag, :git_cmd
def initialize(filename:, line_numbers: nil, left_justify: false,
@tag = tag
@git_cmd = git_cmd
end
# ...

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@sandimetz May 2018
class Listing
def initialize(filename:, line_numbers: nil, left_justify: false,
@left_just = left_justify
@tag = tag
@git_cmd = git_cmd
end
# ...

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@sandimetz May 2018
class Listing
# ...

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@sandimetz May 2018
class Listing
# ...
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
if line_numbers
end
all_lines
end

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@sandimetz May 2018
class Listing
# ...
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
if line_numbers
end
all_lines
end Yup

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@sandimetz May 2018
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
if line_numbers
end
all_lines
end

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@sandimetz May 2018
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
if line_numbers
lines_to_print(all_lines)
else
all_lines
end
end

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@sandimetz May 2018
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
end

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@sandimetz May 2018
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
return justify(subset)
end
subset
end

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@sandimetz May 2018
def justify(lines)
lines.map {|line| line.slice(num_leading_spaces_to_remove(lines)..-1) || ""}
end
def num_leading_spaces_to_remove(lines)
@num ||=
lines.reduce(999999) {|current_min, line|
line.empty? ? current_min : [current_min, num_leading_spaces(line)].min
}
end
def num_leading_spaces(line)
line[/\A */].size
end

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@sandimetz May 2018
def justify(lines)
lines.map {|line| line.slice(num_leading_spaces_to_remove(lines)..-1) || ""}
end
@num ||=
}
end
line[/\A */].size
end
Ouch

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@sandimetz May 2018
Progression

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@sandimetz May 2018
1 File or Git Tag

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@sandimetz May 2018
class Listing
@tag = tag
@git_cmd = git_cmd
end
def lines
if git_cmd
else
end
end
end
class GitCmd
def show
end
private
def git_dir
end
end
1
Lines: 29

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@sandimetz May 2018
class Listing
@tag = tag
@git_cmd = git_cmd
end
def lines
if git_cmd
else
end
end
end
class GitCmd
def show
end
private
def git_dir
end
end
1

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@sandimetz May 2018
class Listing
@tag = tag
@git_cmd = git_cmd
end
def lines
if git_cmd
else
end
end
end
class GitCmd
def show
end
private
def git_dir
end
end
1
Execution
Paths: 2

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@sandimetz May 2018
class Listing
@tag = tag
@git_cmd = git_cmd
end
def lines
if git_cmd
else
end
end
end
class GitCmd
def show
end
private
def git_dir
end
end
1

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@sandimetz May 2018
2All or Some Lines

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@sandimetz May 2018
class Listing
def initialize(filename:, line_numbers: nil, repository: nil, tag: nil, git_cmd: nil)
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
if line_numbers
end
all_lines
end
private
def git_lines
end
def file_lines
end
}.flatten.compact
end
end
class GitCmd
def show
end
private
def git_dir
end
end
2
Lines: 50

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@sandimetz May 2018
class Listing
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
if line_numbers
end
all_lines
end
private
def git_lines
end
def file_lines
end
}.flatten.compact
end
end
class GitCmd
def show
end
private
def git_dir
end
end
2
Execution
Paths:

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@sandimetz May 2018
class Listing
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
if line_numbers
end
all_lines
end
private
def git_lines
end
def file_lines
end
}.flatten.compact
end
end
class GitCmd
def show
end
private
def git_dir
end
end
2
Execution
Paths: 4

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@sandimetz May 2018
class Listing
@tag = tag
@git_cmd = git_cmd
end
def lines
if git_cmd
else
end
end
end
class GitCmd
def show
end
private
def git_dir
end
end
class Listing
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
if line_numbers
end
all_lines
end
private
def git_lines
end
def file_lines
end
}.flatten.compact
end
end
class GitCmd
def show
end
private
def git_dir
end
end
1 2

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@sandimetz May 2018
3Code Line or Comment

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@sandimetz May 2018
class Listing
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
if line_numbers
end
all_lines
end
private
def git_lines
end
def file_lines
end
(" " * num_spaces) + "# ..."
else
range_of_line_numbers = (edges.min.to_i..edges.max.to_i).to_a
range_of_line_numbers.collect {|i| all_lines[i - 1]}.compact
end
}.flatten.compact
end
end
class GitCmd
def show
end
private
def git_dir
end
end
3
Lines: 55

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@sandimetz May 2018
class Listing
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
if line_numbers
end
all_lines
end
private
def git_lines
end
def file_lines
end
(" " * num_spaces) + "# ..."
else
end
}.flatten.compact
end
end
class GitCmd
def show
end
private
def git_dir
end
end
3
Execution
Paths:

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@sandimetz May 2018
class Listing
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
if line_numbers
end
all_lines
end
private
def git_lines
end
def file_lines
end
(" " * num_spaces) + "# ..."
else
end
}.flatten.compact
end
end
class GitCmd
def show
end
private
def git_dir
end
end
3
Execution
Paths: 8

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@sandimetz May 2018
class Listing
@tag = tag
@git_cmd = git_cmd
end
def lines
if git_cmd
else
end
end
end
class GitCmd
def show
end
private
def git_dir
end
end
class Listing
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
if line_numbers
end
all_lines
end
private
def git_lines
end
def file_lines
end
}.flatten.compact
end
end
class GitCmd
def show
end
private
def git_dir
end
end
1 2
class Listing
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
if line_numbers
end
all_lines
end
private
def git_lines
end
def file_lines
end
(" " * num_spaces) + "# ..."
else
end
}.flatten.compact
end
end
class GitCmd
def show
end
private
def git_dir
end
end
3

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@sandimetz May 2018
4Raw or Left Just

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@sandimetz May 2018
class Listing
def initialize(filename:, line_numbers: nil, left_justify: false, repository: nil, tag: nil, git_cmd: nil)
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
private
####################
# Reading
####################
def git_lines
end
def file_lines
end
####################
# Subsetting
####################
(" " * num_spaces) + "# ..."
else
end
}.flatten.compact
end
####################
# Justification
####################
def justify(lines)
lines.map {|line| line.slice(num_leading_spaces_to_remove(lines)..-1) || "" }
end
@num ||=
}
end
line[/\A */].size
end
end
class GitCmd
def show
end
private
def git_dir
end
end
# plus 90+ lines of error handling
4
Lines: 83

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@sandimetz May 2018
class Listing
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
private
####################
# Reading
####################
def git_lines
end
def file_lines
end
####################
# Subsetting
####################
(" " * num_spaces) + "# ..."
else
end
}.flatten.compact
end
####################
# Justification
####################
def justify(lines)
end
@num ||=
}
end
line[/\A */].size
end
end
class GitCmd
def show
end
private
def git_dir
end
end
4
Execution
Paths:

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@sandimetz May 2018
class Listing
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
private
####################
# Reading
####################
def git_lines
end
def file_lines
end
####################
# Subsetting
####################
(" " * num_spaces) + "# ..."
else
end
}.flatten.compact
end
####################
# Justification
####################
def justify(lines)
end
@num ||=
}
end
line[/\A */].size
end
end
class GitCmd
def show
end
private
def git_dir
end
end
4
Execution
Paths: 16

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@sandimetz May 2018
class Listing
@tag = tag
@git_cmd = git_cmd
end
def lines
if git_cmd
else
end
end
end
class GitCmd
def show
end
private
def git_dir
end
end
class Listing
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
if line_numbers
end
all_lines
end
private
def git_lines
end
def file_lines
end
}.flatten.compact
end
end
class GitCmd
def show
end
private
def git_dir
end
end
1 2
class Listing
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
if line_numbers
end
all_lines
end
private
def git_lines
end
def file_lines
end
(" " * num_spaces) + "# ..."
else
end
}.flatten.compact
end
end
class GitCmd
def show
end
private
def git_dir
end
end
3
class Listing
def initialize(filename:, line_numbers: nil, left_justify: false, repository: nil, tag:
nil, git_cmd: nil)
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
private
####################
# Reading
####################
def git_lines
end
def file_lines
end
####################
# Subsetting
####################
(" " * num_spaces) + "# ..."
else
end
}.flatten.compact
end
####################
# Justification
####################
def justify(lines)
end
@num ||=
}
end
line[/\A */].size
end
end
class GitCmd
def show
end
private
def git_dir
end
end
4

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@sandimetz May 2018

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@sandimetz May 2018
Ouch

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@sandimetz May 2018

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@sandimetz May 2018
Ouch

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@sandimetz May 2018

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@sandimetz May 2018
Ouch

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@sandimetz May 2018

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@sandimetz May 2018
What brought you success

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@sandimetz May 2018
What brought you success
will doom you to failure.

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@sandimetz May 2018
Aﬀordances

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@sandimetz May 2018
"Doorknob" by photonooner CC BY-NC-ND

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@sandimetz May 2018
"Door Handle" by www.trek.today CC BY-NC-ND

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@sandimetz May 2018
"Door Handle" by www.trek.today CC BY-NC-ND
"pull" by various brennemans CC BY-SA

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@sandimetz May 2018
I'm a loser and lost the attribution. Sorry.

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@sandimetz May 2018
"pull" by greenkozi CC BY-NC-ND

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@sandimetz May 2018
"pull" by greenkozi CC BY-NC-ND
"door push plate" by stu_spivack CC BY-SA

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@sandimetz May 2018
OO
Aﬀords

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@sandimetz May 2018
OO
Aﬀords
Anthropomorphic

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@sandimetz May 2018
OO
Aﬀords
Anthropomorphic
Polymorphic

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@sandimetz May 2018
OO
Aﬀords
Anthropomorphic
Polymorphic
Loosely-coupled

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@sandimetz May 2018
OO
Aﬀords
Anthropomorphic
Polymorphic
Loosely-coupled
Role-playing

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@sandimetz May 2018
OO
Aﬀords
Anthropomorphic
Polymorphic
Loosely-coupled
Role-playing
Factory-created

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@sandimetz May 2018
OO
Aﬀords
Anthropomorphic
Polymorphic
Loosely-coupled
Role-playing
Factory-created
Message-sending

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@sandimetz May 2018
OO
Aﬀords
Anthropomorphic
Polymorphic
Loosely-coupled
Role-playing
Factory-created
Message-sending
Objects

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@sandimetz May 2018
Anthropomorphism

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@sandimetz May 2018
Anthropomorphism
-the attribution of human traits, emotions or
intentions to non-human entities.

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@sandimetz May 2018

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@sandimetz May 2018
Polymorphism

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@sandimetz May 2018
Polymorphism
-the condition of occurring in
several diﬀerent forms

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@sandimetz May 2018

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@sandimetz May 2018
Loosely-Coupled

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@sandimetz May 2018
Loosely-Coupled
-objects strive for independence

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@sandimetz May 2018

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@sandimetz May 2018
Role-playing

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@sandimetz May 2018
Role-playing
-objects are more players of their roles
than instances of their types

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@sandimetz May 2018

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@sandimetz May 2018
Factory-created

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@sandimetz May 2018
Factory-created
-factories hide the rules for picking
the right player of a role

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@sandimetz May 2018

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@sandimetz May 2018
Message-sending

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@sandimetz May 2018
Message-sending
-I know what I want,
you know how to do it

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@sandimetz May 2018

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@sandimetz May 2018
OO
Aﬀords
Anthropomorphic
Polymorphic
Loosely-coupled
Role-playing
Factory-created
Message-sending
Objects

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@sandimetz May 2018
Resolution

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@sandimetz May 2018
Where all ends well
Resolution

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@sandimetz May 2018
class Listing
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end

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@sandimetz May 2018
class Listing
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
2

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@sandimetz May 2018
class Listing
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
2
2x2

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@sandimetz May 2018
class Listing
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
2
2x2
2x2x2

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@sandimetz May 2018
class Listing
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
specs = line_numbers.gsub(/[‘|’]/,
num_spaces = spec.delete("#").
(" " * num_spaces) + "# ..."
else
edges = spec.split('-').collec
range_of_line_numbers = (edges
range_of_line_numbers.collect
end
}.flatten.compact
end
2
2x2
2x2x2

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@sandimetz May 2018
class Listing
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
specs = line_numbers.gsub(/[‘|’]/,
num_spaces = spec.delete("#").
(" " * num_spaces) + "# ..."
else
edges = spec.split('-').collec
range_of_line_numbers = (edges
range_of_line_numbers.collect
end
}.flatten.compact
end
2
2x2
2x2x2
2x2x2x2

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@sandimetz May 2018
class Listing
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end

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@sandimetz May 2018
class Listing
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
If you know enough
to inject this

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@sandimetz May 2018
class Listing
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
Inject a
smarter
thing

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@sandimetz May 2018
class Listing
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
1 File or Git Tag

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@sandimetz May 2018
class Listing
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
1 Role = Source

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@sandimetz May 2018
Source

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@sandimetz May 2018
Source #lines

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@sandimetz May 2018
Source #lines
File
Source
GitTag
Source

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@sandimetz May 2018
class FileSource
end
class GitTagSource
end
S
O
U
R
C
E
S

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@sandimetz May 2018
class FileSource
def lines
end
# ...
end
class GitTagSource
def lines
end
# ...
end
S
O
U
R
C
E
S

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@sandimetz May 2018
class FileSource
def lines
end
# ...
end
class GitTagSource
def lines
end
# ...
end
S
O
U
R
C
E
S
Polymorphism

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@sandimetz May 2018
class FileSource
def lines
end
# ...
end
class GitTagSource
def lines
end
# ...
end
S
O
U
R
C
E
S

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@sandimetz May 2018
Isolate the things
you want to vary

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@sandimetz May 2018
class Listing
def initialize(filename:, line_numbers: nil, left_justify: false, repository: nil, tag: nil,
git_cmd: nil)
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset = # ...
def git_lines
end
def file_lines
end

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@sandimetz May 2018
def git_lines
end
def file_lines
end
v
v
v
class Listing
def initialize(filename:, line_numbers: nil, left_justify: false, repository: nil, tag: nil,
git_cmd: nil)
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset = # ...

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@sandimetz May 2018
class Listing
attr_reader :line_numbers, :left_just
def initialize( line_numbers: nil, left_justify: false)
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset = # ...

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@sandimetz May 2018
class Listing
attr_reader :line_numbers, :left_just
def initialize( line_numbers: nil, left_justify: false)
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset = # ...
Inject a Source

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@sandimetz May 2018
class Listing
attr_reader :source, :line_numbers, :left_just
def initialize(source:, line_numbers: nil, left_justify: false)
@source = source
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset = # ...

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@sandimetz May 2018
class Listing
@source = source
end
def lines
all_lines = source.lines
subset = # ...

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@sandimetz May 2018
class Listing
@source = source
end
def lines
subset = # ...
Execution
Paths: 16?

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@sandimetz May 2018
class Listing
@source = source
end
def lines
subset = # ...
Execution
Paths: 8

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@sandimetz May 2018
Push conditionals
back on the stack

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@sandimetz May 2018
class Listing
@source = source
end
def lines
subset =

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@sandimetz May 2018
class Listing
@source = source
end
def lines
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end

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@sandimetz May 2018
class Listing
@source = source
end
def lines
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
2
All or Some Lines

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@sandimetz May 2018
class Listing
@source = source
end
def lines
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
2
Subset

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@sandimetz May 2018
class Listing
@source = source
end
def lines
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
Inject a smarter thing

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@sandimetz May 2018
Subset

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@sandimetz May 2018
Subset #lines

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@sandimetz May 2018
Subset #lines
Everything
Line
Number

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@sandimetz May 2018
module Subset
class Everything
end
class LineNumber
end
end
S
U
B
S
E
T

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@sandimetz May 2018
module Subset
class Everything
end
class LineNumber
end
S
U
B
S
E
T

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@sandimetz May 2018
module Subset
class Everything
def lines(everything)
end
end
class LineNumber
end
S
U
B
S
E
T

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@sandimetz May 2018
module Subset
class Everything
everything
end
end
class LineNumber
end
S
U
B
S
E
T

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@sandimetz May 2018
module Subset
class Everything
end
class LineNumber
end
S
U
B
S
E
T

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@sandimetz May 2018
module Subset
class Everything; end
class LineNumber
end
S
U
B
S
E
T

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@sandimetz May 2018
module Subset
class LineNumber
# ...
def lines_to_print(possibilities)
specs = line_numbers.gsub(/[‘|’]/, "").gsub(/ /
(" " * num_spaces) + "# ..."
else
range_of_line_numbers = (edges.min.to_i..ed
range_of_line_numbers.collect {|i| all_line
end
}.flatten.compact
end
end
S
U
B
S
E
T

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@sandimetz May 2018
module Subset
class LineNumber
# ...
def lines(possibilities)
(" " * num_spaces) + "# ..."
else
end
}.flatten.compact
end
end
S
U
B
S
E
T

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@sandimetz May 2018
module Subset
class LineNumber
# ...
(" " * num_spaces) + "# ..."
else
end
}.flatten.compact
end
end
S
U
B
S
E
T
?

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@sandimetz May 2018
class Listing
@source = source
end
def lines
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
specs = line_numbers.gsub(/[
num_spaces = spec.delete
(" " * num_spaces) + "#
else
edges = spec.split('-').
range_of_line_numbers =
range_of_line_numbers.co
end
}.flatten.compact
end

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@sandimetz May 2018
class Listing
attr_reader :source, :left_just
def initialize(source:, left_justify: false)
@source = source
end
def lines
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end

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@sandimetz May 2018
class Listing
attr_reader :source, :subsetter, :left_just
def initialize(source:, subsetter:, left_justify: false)
@source = source
end
def lines
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end

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@sandimetz May 2018
class Listing
@source = source
@subsetter = subsetter
end
def lines
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end

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@sandimetz May 2018
class Listing
@source = source
end
def lines
subset = subsetter.lines(all_lines)
if left_just
end
subset
end

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@sandimetz May 2018
class Listing
@source = source
end
def lines
subset = subsetter.lines(source.lines)
if left_just
end
subset
end

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@sandimetz May 2018
class Listing
@source = source
end
def lines
if left_just
end
subset
end
Execution
Paths: 4

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@sandimetz May 2018
Dependency injection
is your friend

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@sandimetz May 2018
As long as
you inject smart things

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@sandimetz May 2018
class Listing
@source = source
end
def lines
if left_just
end
subset
end

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@sandimetz May 2018
class Listing
@source = source
end
def lines
if left_just
end
subset
end
4 Raw or Left Just

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@sandimetz May 2018
class Listing
@source = source
end
def lines
if left_just
end
subset
end
4 Justiﬁer

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@sandimetz May 2018
Justiﬁer

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@sandimetz May 2018
Justiﬁer #justify

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@sandimetz May 2018
Justiﬁer #justify
None
Block
Left

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@sandimetz May 2018
module Justification
class None
def justify(lines)
lines
end
end
class BlockLeft
def justify(lines)
lines.map {|line| line.slice(num_leading_spaces
end
def num_leading_spaces_to_remove; end
def num_leading_spaces(line); end
end
end
J
U
S
T
I
F
I
E
R

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@sandimetz May 2018
class Listing
@source = source
end
def lines
if left_just
end
subset
end
end

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@sandimetz May 2018
class Listing
attr_reader :source, :subsetter, :justifier
def initialize(source:, subsetter:, justifier:)
@source = source
@justifier = justifier
end
def lines
if left_just
end
subset
end
end

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@sandimetz May 2018
class Listing
@source = source
end
def lines
justifier.justify(subset)
end
end

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@sandimetz May 2018
class Listing
@source = source
end
def lines
justifier.justify(subsetter.lines(source.lines))
end
end

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@sandimetz May 2018
class Listing
@source = source
end
def lines
end
end

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@sandimetz May 2018
But, conditionals?

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@sandimetz May 2018
class Listing
@source = source
end
def lines
end
end
3
Code Line or
Comment

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@sandimetz May 2018
class Listing
@source = source
end
def lines
end
end
module Subset
class LineNumber
specs = line_numbers.gsub(/[‘|’]/, "
num_spaces = spec.delete("#").to
(" " * num_spaces) + "# ..."
else
edges = spec.split('-').collect(
range_of_line_numbers = (edges.m
range_of_line_numbers.collect {|
end
}.flatten.compact
end
3
Code Line or
Comment

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@sandimetz May 2018
class Listing
@source = source
end
def lines
end
end
module Subset
class LineNumber
specs = line_numbers.gsub(/[‘|’]/, "
num_spaces = spec.delete("#").to
(" " * num_spaces) + "# ..."
else
edges = spec.split('-').collect(
range_of_line_numbers = (edges.m
range_of_line_numbers.collect {|
end
}.flatten.compact
end
3
Clump

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@sandimetz May 2018
Clump

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@sandimetz May 2018
Clump #lines

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@sandimetz May 2018
Clump #lines
Comment
Line
Number

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@sandimetz May 2018
class Clump
# initialize with spec and input
class Comment < Clump
def lines
(" " * num_spaces) + "# ..."
end
end
class LineNumber < Clump
def lines
expand_clump(spec).collect {|i| input[i - 1]}.c
end
def expand_clump(spec)
# ...
end
end
end
C
L
U
M
P

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@sandimetz May 2018
module Subset
class LineNumber
(" " * num_spaces) + "# ..."
else
end
}.flatten.compact
end
S
U
B
S
E
T

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@sandimetz May 2018
module Subset
class LineNumber
else
end
}.flatten.compact
end
S
U
B
S
E
T

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@sandimetz May 2018
module Subset
class LineNumber
Clump::Comment.new(...).lines
else
end
}.flatten.compact
end
S
U
B
S
E
T

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@sandimetz May 2018
module Subset
class LineNumber
else
Clump::LineNumber.new(...).lines
end
}.flatten.compact
end
S
U
B
S
E
T

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@sandimetz May 2018
module Subset
class LineNumber
else
end
}.flatten.compact
end
Polymorphic
S
U
B
S
E
T

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@sandimetz May 2018
module Subset
class LineNumber
else
end
}.flatten.compact
end
Role-playing
S
U
B
S
E
T

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@sandimetz May 2018
module Subset
class LineNumber
else
end
}.flatten.compact
end
Rule ??
S
U
B
S
E
T

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@sandimetz May 2018
module Subset
class LineNumber
else
end
}.flatten.compact
end
Tightly-coupled
S
U
B
S
E
T

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@sandimetz May 2018
module Subset
class LineNumber
else
end
}.flatten.compact
end
S
U
B
S
E
T

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@sandimetz May 2018
module Subset
class LineNumber
else
end
}.flatten.compact
end
Factory!
S
U
B
S
E
T

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@sandimetz May 2018
class Clump
def self.for(spec:, possibilities: [])
Clump::Comment
else
Clump::LineNumber
end.new(spec: spec, input: possibilities)
end
# ...
end
C
L
U
M
P

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@sandimetz May 2018
class Clump
def self.lines(spec:, possibilities: [])
self.for(spec: spec, possibilities: possibilities).lines
end
Clump::Comment
else
Clump::LineNumber
end
# ...
end
C
L
U
M
P

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@sandimetz May 2018
class Clump
end
Clump::Comment
else
Clump::LineNumber
end
# ...
end
C
L
U
M
P
Factory-created

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@sandimetz May 2018
module Subset
class LineNumber
else
end
}.flatten.compact
end
S
U
B
S
E
T

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@sandimetz May 2018
module Subset
class LineNumber
}.flatten.compact
end
S
U
B
S
E
T

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@sandimetz May 2018
module Subset
class LineNumber
Clump.lines(spec: spec, possibilities: possibilities)
}.flatten.compact
end
S
U
B
S
E
T

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@sandimetz May 2018
Reprise

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@sandimetz May 2018
class Listing
@tag = tag
@git_cmd = git_cmd
end
def lines
if git_cmd
else
end
end
end
class GitCmd
def show
end
private
def git_dir
end
end
class Listing
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
if line_numbers
end
all_lines
end
private
def git_lines
end
def file_lines
end
}.flatten.compact
end
end
class GitCmd
def show
end
private
def git_dir
end
end
1 2
class Listing
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
if line_numbers
end
all_lines
end
private
def git_lines
end
def file_lines
end
(" " * num_spaces) + "# ..."
else
end
}.flatten.compact
end
end
class GitCmd
def show
end
private
def git_dir
end
end
3
class Listing
nil, git_cmd: nil)
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
private
####################
# Reading
####################
def git_lines
end
def file_lines
end
####################
# Subsetting
####################
(" " * num_spaces) + "# ..."
else
end
}.flatten.compact
end
####################
# Justification
####################
def justify(lines)
end
@num ||=
}
end
line[/\A */].size
end
end
class GitCmd
def show
end
private
def git_dir
end
end
4

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@sandimetz May 2018
class Listing
nil, git_cmd: nil)
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
private
####################
# Reading
####################
def git_lines
end
def file_lines
end
####################
# Subsetting
####################
(" " * num_spaces) + "# ..."
else
end
}.flatten.compact
end
####################
# Justification
####################
def justify(lines)
end
@num ||=
}
end
line[/\A */].size
end
end
class GitCmd
def show
end
private
def git_dir
end
end
Lines: 83
Execution
Paths: 16
Procedure

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@sandimetz May 2018
class Listing
nil, git_cmd: nil)
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
private
####################
# Reading
####################
def git_lines
end
def file_lines
end
####################
# Subsetting
####################
(" " * num_spaces) + "# ..."
else
end
}.flatten.compact
end
####################
# Justification
####################
def justify(lines)
end
@num ||=
}
end
line[/\A */].size
end
end
class GitCmd
def show
end
private
def git_dir
end
end
Lines: 83
Execution
Paths: 16
Procedure OO

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@sandimetz May 2018
class Listing
nil, git_cmd: nil)
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
private
####################
# Reading
####################
def git_lines
end
def file_lines
end
####################
# Subsetting
####################
(" " * num_spaces) + "# ..."
else
end
}.flatten.compact
end
####################
# Justification
####################
def justify(lines)
end
@num ||=
}
end
line[/\A */].size
end
end
class GitCmd
def show
end
private
def git_dir
end
end
Lines: 83
Execution
Paths: 16
Procedure
module Source
class File
attr_reader :filename
def initialize(filename:)
end
def lines
::File.read(filename).split("\n")
end
end
class GitTag
def self.git_cmd
GitCmd.new
end
attr_reader :filename, :tag, :repository, :git_cmd
def initialize(filename:, repository:, tag:, git_cmd: self.class.git_cmd)
@git_cmd = git_cmd
end
def lines
end
class GitCmd
def show
end
def git_dir
end
end
end
end
Source:
File
GitTag
OO

View Slide

@sandimetz May 2018
class Listing
nil, git_cmd: nil)
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
private
####################
# Reading
####################
def git_lines
end
def file_lines
end
####################
# Subsetting
####################
(" " * num_spaces) + "# ..."
else
end
}.flatten.compact
end
####################
# Justification
####################
def justify(lines)
end
@num ||=
}
end
line[/\A */].size
end
end
class GitCmd
def show
end
private
def git_dir
end
end
Lines: 83
Execution
Paths: 16
Procedure
module Source
class File
end
def lines
end
end
class GitTag
def self.git_cmd
GitCmd.new
end
@git_cmd = git_cmd
end
def lines
end
class GitCmd
def show
end
def git_dir
end
end
end
end
OO
module Subset
class Everything
everything
end
end
class LineNumber
attr_reader :line_numbers
def initialize(line_numbers:)
end
clump_specs.collect {|spec| clump_for(spec, possibilities) }.flatten.compact
end
def clump_specs
line_numbers.gsub(/[‘|’]/, "").gsub(/ /,'').split(",")
end
def clump_for(spec, possibilities)
end
end
end
Subset:
Everything
LineNumber
Source:

View Slide

@sandimetz May 2018
class Listing
nil, git_cmd: nil)
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
private
####################
# Reading
####################
def git_lines
end
def file_lines
end
####################
# Subsetting
####################
(" " * num_spaces) + "# ..."
else
end
}.flatten.compact
end
####################
# Justification
####################
def justify(lines)
end
@num ||=
}
end
line[/\A */].size
end
end
class GitCmd
def show
end
private
def git_dir
end
end
Lines: 83
Execution
Paths: 16
Procedure
module Source
class File
end
def lines
end
end
class GitTag
def self.git_cmd
GitCmd.new
end
@git_cmd = git_cmd
end
def lines
end
class GitCmd
def show
end
def git_dir
end
end
end
end
OO
module Subset
class Everything
everything
end
end
class LineNumber
end
end
def clump_specs
end
end
end
end
Subset:
Source:
class Clump
end
Clump::Comment
else
Clump::LineNumber
end
attr_reader :spec, :input
def initialize(spec:, input: [])
@spec = spec
@input = input
end
def lines
expand_clump(spec).collect {|i| input[i - 1]}.compact
end
(edges.min.to_i..edges.max.to_i).to_a
end
end
def lines
(" " * num_spaces) + "# ..."
end
end
end
Clump:
Comment
LineNumber

View Slide

@sandimetz May 2018
class Listing
nil, git_cmd: nil)
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
private
####################
# Reading
####################
def git_lines
end
def file_lines
end
####################
# Subsetting
####################
(" " * num_spaces) + "# ..."
else
end
}.flatten.compact
end
####################
# Justification
####################
def justify(lines)
end
@num ||=
}
end
line[/\A */].size
end
end
class GitCmd
def show
end
private
def git_dir
end
end
Lines: 83
Execution
Paths: 16
Procedure
module Source
class File
end
def lines
end
end
class GitTag
def self.git_cmd
GitCmd.new
end
@git_cmd = git_cmd
end
def lines
end
class GitCmd
def show
end
def git_dir
end
end
end
end
OO
module Subset
class Everything
everything
end
end
class LineNumber
end
end
def clump_specs
end
end
end
end
Subset:
Source:
class Clump
end
Clump::Comment
else
Clump::LineNumber
end
@spec = spec
@input = input
end
def lines
end
def expand_spec(spec)
end
end
def lines
(" " * num_spaces) + "# ..."
end
end
end
Clump:
class None
def self.justify(lines)
lines
end
end
class BlockLeft
new(lines).justify
end
attr_reader :lines
def initialize(lines)
@lines = lines
end
def justify
lines.map {|line| line.slice(num_leading_spaces_to_remove..-1) || "" }
end
private
def num_leading_spaces_to_remove
@num ||=
}
end
line[/\A */].size
end
end
end
Justiﬁcation:
None
BlockLeft

View Slide

@sandimetz May 2018
class Listing
nil, git_cmd: nil)
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
private
####################
# Reading
####################
def git_lines
end
def file_lines
end
####################
# Subsetting
####################
(" " * num_spaces) + "# ..."
else
end
}.flatten.compact
end
####################
# Justification
####################
def justify(lines)
end
@num ||=
}
end
line[/\A */].size
end
end
class GitCmd
def show
end
private
def git_dir
end
end
Lines: 83
Execution
Paths: 16
Procedure
module Source
class File
end
def lines
end
end
class GitTag
def self.git_cmd
GitCmd.new
end
@git_cmd = git_cmd
end
def lines
end
class GitCmd
def show
end
def git_dir
end
end
end
end
OO
module Subset
class Everything
everything
end
end
class LineNumber
end
end
def clump_specs
end
end
end
end
Subset:
Source:
class Clump
end
Clump::Comment
else
Clump::LineNumber
end
@spec = spec
@input = input
end
def lines
end
end
end
def lines
(" " * num_spaces) + "# ..."
end
end
end
Clump:
class None
lines
end
end
class BlockLeft
new(lines).justify
end
attr_reader :lines
@lines = lines
end
def justify
end
private
@num ||=
}
end
line[/\A */].size
end
end
end
Justiﬁcation:
class Listing
@source = source
end
def lines
end
end

View Slide

@sandimetz May 2018
class Listing
nil, git_cmd: nil)
@tag = tag
@git_cmd = git_cmd
end
def lines
all_lines =
if git_cmd
git_lines
else
file_lines
end
subset =
if line_numbers
else
all_lines
end
if left_just
end
subset
end
private
####################
# Reading
####################
def git_lines
end
def file_lines
end
####################
# Subsetting
####################
(" " * num_spaces) + "# ..."
else
end
}.flatten.compact
end
####################
# Justification
####################
def justify(lines)
end
@num ||=
}
end
line[/\A */].size
end
end
class GitCmd
def show
end
private
def git_dir
end
end
Lines: 83
Execution
Paths: 16
Procedure
module Source
class File
end
def lines
end
end
class GitTag
def self.git_cmd
GitCmd.new
end
@git_cmd = git_cmd
end
def lines
end
class GitCmd
def show
end
def git_dir
end
end
end
end
OO
module Subset
class Everything
everything
end
end
class LineNumber
end
end
def clump_specs
end
end
end
end
Subset:
Source:
class Clump
end
Clump::Comment
else
Clump::LineNumber
end
@spec = spec
@input = input
end
def lines
end
end
end
def lines
(" " * num_spaces) + "# ..."
end
end
end
Clump:
class None
lines
end
end
class BlockLeft
new(lines).justify
end
attr_reader :lines
@lines = lines
end
def justify
end
private
@num ||=
}
end
line[/\A */].size
end
end
end
Justiﬁcation:
class Listing
@source = source
end
def lines
end
end
Factories

View Slide

@sandimetz May 2018
Lines: 83
Execution
Paths: 16
Procedure
module Source
class File
end
def lines
end
end
class GitTag
def self.git_cmd
GitCmd.new
end
@git_cmd = git_cmd
end
def lines
end
class GitCmd
def show
end
def git_dir
end
end
end
end
OO
module Subset
class Everything
everything
end
end
class LineNumber
end
end
def clump_specs
end
end
end
end
Subset:
Source:
class Clump
end
Clump::Comment
else
Clump::LineNumber
end
@spec = spec
@input = input
end
def lines
end
end
end
def lines
(" " * num_spaces) + "# ..."
end
end
end
Clump:
class None
lines
end
end
class BlockLeft
new(lines).justify
end
attr_reader :lines
@lines = lines
end
def justify
end
private
@num ||=
}
end
line[/\A */].size
end
end
end
Justiﬁcation:
class Listing
@source = source
end
def lines
end
end
Factories

View Slide

@sandimetz May 2018
Lines: 83
Execution
Paths: 16
module Source
class File
end
def lines
end
end
class GitTag
def self.git_cmd
GitCmd.new
end
@git_cmd = git_cmd
end
def lines
end
class GitCmd
def show
end
def git_dir
end
end
end
end
OO
module Subset
class Everything
everything
end
end
class LineNumber
end
end
def clump_specs
end
end
end
end
Subset:
Source:
class Clump
end
Clump::Comment
else
Clump::LineNumber
end
@spec = spec
@input = input
end
def lines
end
end
end
def lines
(" " * num_spaces) + "# ..."
end
end
end
Clump:
class None
lines
end
end
class BlockLeft
new(lines).justify
end
attr_reader :lines
@lines = lines
end
def justify
end
private
@num ||=
}
end
line[/\A */].size
end
end
end
Justiﬁcation:
class Listing
@source = source
end
def lines
end
end
Factories
Procedure

View Slide

@sandimetz May 2018
Lines: 83
Execution
Paths: 16
module Source
class File
end
def lines
end
end
class GitTag
def self.git_cmd
GitCmd.new
end
@git_cmd = git_cmd
end
def lines
end
class GitCmd
def show
end
def git_dir
end
end
end
end
OO
module Subset
class Everything
everything
end
end
class LineNumber
end
end
def clump_specs
end
end
end
end
Subset:
Source:
class Clump
end
Clump::Comment
else
Clump::LineNumber
end
@spec = spec
@input = input
end
def lines
end
end
end
def lines
(" " * num_spaces) + "# ..."
end
end
end
Clump:
class None
lines
end
end
class BlockLeft
new(lines).justify
end
attr_reader :lines
@lines = lines
end
def justify
end
private
@num ||=
}
end
line[/\A */].size
end
end
end
Justiﬁcation:
class Listing
@source = source
end
def lines
end
end
Factories
Procedure
Total Lines: 134

View Slide

@sandimetz May 2018
Lines: 83
Execution
Paths: 16
module Source
class File
end
def lines
end
end
class GitTag
def self.git_cmd
GitCmd.new
end
@git_cmd = git_cmd
end
def lines
end
class GitCmd
def show
end
def git_dir
end
end
end
end
OO
module Subset
class Everything
everything
end
end
class LineNumber
end
end
def clump_specs
end
end
end
end
Subset:
Source:
class Clump
end
Clump::Comment
else
Clump::LineNumber
end
@spec = spec
@input = input
end
def lines
end
end
end
def lines
(" " * num_spaces) + "# ..."
end
end
end
Clump:
class None
lines
end
end
class BlockLeft
new(lines).justify
end
attr_reader :lines
@lines = lines
end
def justify
end
private
@num ||=
}
end
line[/\A */].size
end
end
end
Justiﬁcation:
class Listing
@source = source
end
def lines
end
end
Factories
Procedure
Total Lines: 134
Execution Paths: 1

View Slide

@sandimetz May 2018
Lines: 83
Execution
Paths: 16
module Source
class File
end
def lines
end
end
class GitTag
def self.git_cmd
GitCmd.new
end
@git_cmd = git_cmd
end
def lines
end
class GitCmd
def show
end
def git_dir
end
end
end
end
OO
module Subset
class Everything
everything
end
end
class LineNumber
end
end
def clump_specs
end
end
end
end
Subset:
Source:
class Clump
end
Clump::Comment
else
Clump::LineNumber
end
@spec = spec
@input = input
end
def lines
end
end
end
def lines
(" " * num_spaces) + "# ..."
end
end
end
Clump:
class None
lines
end
end
class BlockLeft
new(lines).justify
end
attr_reader :lines
@lines = lines
end
def justify
end
private
@num ||=
}
end
line[/\A */].size
end
end
end
Justiﬁcation:
class Listing
@source = source
end
def lines
end
end
Factories
Procedure
Classes: 9
Total Lines: 134
Execution Paths: 1

View Slide

@sandimetz May 2018
Lines: 83
Execution
Paths: 16
module Source
class File
end
def lines
end
end
class GitTag
def self.git_cmd
GitCmd.new
end
@git_cmd = git_cmd
end
def lines
end
class GitCmd
def show
end
def git_dir
end
end
end
end
OO
module Subset
class Everything
everything
end
end
class LineNumber
end
end
def clump_specs
end
end
end
end
Subset:
Source:
class Clump
end
Clump::Comment
else
Clump::LineNumber
end
@spec = spec
@input = input
end
def lines
end
end
end
def lines
(" " * num_spaces) + "# ..."
end
end
end
Clump:
class None
lines
end
end
class BlockLeft
new(lines).justify
end
attr_reader :lines
@lines = lines
end
def justify
end
private
@num ||=
}
end
line[/\A */].size
end
end
end
Justiﬁcation:
class Listing
@source = source
end
def lines
end
end
Factories
Procedure
Classes: 9
Biggest: 18 loc
Total Lines: 134
Execution Paths: 1

View Slide

@sandimetz May 2018
Lines: 83
Execution
Paths: 16
module Source
class File
end
def lines
end
end
class GitTag
def self.git_cmd
GitCmd.new
end
@git_cmd = git_cmd
end
def lines
end
class GitCmd
def show
end
def git_dir
end
end
end
end
OO
module Subset
class Everything
everything
end
end
class LineNumber
end
end
def clump_specs
end
end
end
end
Subset:
Source:
class Clump
end
Clump::Comment
else
Clump::LineNumber
end
@spec = spec
@input = input
end
def lines
end
end
end
def lines
(" " * num_spaces) + "# ..."
end
end
end
Clump:
class None
lines
end
end
class BlockLeft
new(lines).justify
end
attr_reader :lines
@lines = lines
end
def justify
end
private
@num ||=
}
end
line[/\A */].size
end
end
end
Justiﬁcation:
class Listing
@source = source
end
def lines
end
end
Factories
Procedure

View Slide

@sandimetz May 2018
class Clump
Clump::Comment
else
Clump::LineNumber
end
# ...
end

View Slide

@sandimetz May 2018
class Clump
Clump::Comment
else
Clump::LineNumber
end
# ...
end
Factories are shared
Factories are isolated
Factories are simple
Factories are ignorable

View Slide

@sandimetz May 2018
module Source
class File
end
def lines
end
end
class GitTag
def self.git_cmd
GitCmd.new
end
@git_cmd = git_cmd
end
def lines
end
class GitCmd
def show
end
def git_dir
end
end
end
end
OO
module Subset
class Everything
everything
end
end
class LineNumber
end
end
def clump_specs
end
end
end
end
Subset:
Source:
class Clump
end
Clump::Comment
else
Clump::LineNumber
end
@spec = spec
@input = input
end
def lines
end
end
end
def lines
(" " * num_spaces) + "# ..."
end
end
end
Clump:
class None
lines
end
end
class BlockLeft
new(lines).justify
end
attr_reader :lines
@lines = lines
end
def justify
end
private
@num ||=
}
end
line[/\A */].size
end
end
end
Justiﬁcation:
class Listing
@source = source
end
def lines
end
end
Factories

View Slide

@sandimetz May 2018
OO
class Listing
@source = source
end
def lines
end
end

View Slide

@sandimetz May 2018
Anthropomorphic
Polymorphic
Loosely-coupled
Role-playing
Factory-created
Message-sending

View Slide

@sandimetz
Thanks
May 2018

View Slide

@sandimetz
http://poodr.com
May 2018

View Slide

@sandimetz
http://99bottlesbook.com
May 2018

View Slide

@sandimetz
Sandi Metz
@sandimetz
http://sandimetz.com
May 2018

View Slide

Polly Want A Message (DeconstructConf)

Polly Want A Message (DeconstructConf)

Sandi Metz

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