all the little things (rubyonales)

@sandimetz Mar 2014
sandi metz
all the little things
Friday, March 7, 14

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@sandimetz Mar 2014
Want better apps?
Friday, March 7, 14

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@sandimetz Mar 2014
make smaller things
Friday, March 7, 14

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@sandimetz Mar 2014
The Gilded Rose Kata
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
attr_reader :name, :quality, :days_remaining
def initialize(name, quality, days_remaining)
@name, @quality, @days_remaining = name, quality, days_remaining
end
def tick
# ...
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @name != 'Aged Brie' && @name != 'Backstage passes to a TAFKAL80ETC c
if @quality > 0
if @name != 'Sulfuras, Hand of Ragnaros'
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @name == 'Backstage passes to a TAFKAL80ETC concert'
if @days_remaining < 11
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
# 21 more lines
def tick
if name != 'Aged Brie' && name != 'Backstage passes to a TAFKAL80ETC concert'
if quality > 0
if name != 'Sulfuras, Hand of Ragnaros'
@quality -‐= 1
end
end
else
if quality < 50
@quality += 1
if name == 'Backstage passes to a TAFKAL80ETC concert'
if days_remaining < 11
if quality < 50
@quality += 1
end
end
if quality < 50
@quality += 1
end
end
end
end
end
@days_remaining -‐= 1
end
if name != "Aged Brie"
if name != 'Backstage passes to a TAFKAL80ETC concert'
if quality > 0
@quality -‐= 1
end
end
else
@quality = quality -‐ quality
end
else
if quality < 50
@quality += 1
end
end
end
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
# 22 previous lines
end
if @name != "Aged Brie"
if @name != 'Backstage passes to a TAFKAL80ETC concert'
if @quality > 0
@quality -‐= 1
end
end
else
@quality = @quality -‐ @quality
end
else
if @quality < 50
@quality += 1
end
end
end
end
def tick
if quality > 0
@quality -‐= 1
end
end
else
if quality < 50
@quality += 1
if quality < 50
@quality += 1
end
end
if quality < 50
@quality += 1
end
end
end
end
end
end
if quality > 0
@quality -‐= 1
end
end
else
end
else
if quality < 50
@quality += 1
end
end
end
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @name != 'Aged Brie' && @name != 'Backstage passes to a TAFKAL80ETC concert'
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
44.7
0
25
50
big conditional
Complexity (Flog)
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
44.7
0
25
50
big conditional
Complexity (Flog)
50
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
44.7
0
25
50
big conditional
Complexity (Flog)
45
tick
50
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
Squint Test
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
changes in shape
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
2
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
changes in color
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
16 if statements
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
16 if statements
7 !=
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
16 if statements
7 !=
2 != with &&
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
16 if statements
7 !=
2 != with &&
3 magic strings
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
16 if statements
7 !=
2 != with &&
3 magic strings
? magic numbers
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
magic strings
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
‘Aged Brie’
magic strings
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
‘Aged Brie’
‘Sulfuras, Hand of Ragnaros’
magic strings
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
‘Aged Brie’
‘Sulfuras, Hand of Ragnaros’
‘Backstage passes
to a TAFKAL80ETC concert’
magic strings
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
it has tests
Friday, March 7, 14

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@sandimetz Mar 2014
# Running:
S..S.S...S..........S....S.....
Fabulous run in 0.002800s, 11071.4286 runs/s, 17857.1429 assertions/s.
31 runs, 50 assertions, 0 failures, 0 errors, 6 skips
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRoseTest < Minitest::Test
def test_normal_item_before_sell_date
def test_normal_item_on_sell_date
def test_normal_item_after_sell_date
def test_normal_item_of_zero_quality
def test_brie_before_sell_date
def test_brie_before_sell_date_with_max_quality
def test_brie_on_sell_date
def test_brie_on_sell_date_near_max_quality
def test_brie_on_sell_date_with_max_quality
def test_brie_after_sell_date
def test_brie_after_sell_date_with_max_quality
def test_sulfuras_before_sell_date
def test_sulfuras_on_sell_date
def test_sulfuras_after_sell_date
def test_backstage_pass_long_before_sell_date
def test_backstage_pass_medium_close_to_sell_date_upper_bound
def test_backstage_pass_medium_close_to_sell_date_upper_bound_at_max_quality
def test_backstage_pass_medium_close_to_sell_date_lower_bound
def test_backstage_pass_medium_close_to_sell_date_lower_bound_at_max_quality
def test_backstage_pass_very_close_to_sell_date_upper_bound
def test_backstage_pass_very_close_to_sell_date_upper_bound_at_max_quality
def test_backstage_pass_very_close_to_sell_date_lower_bound
def test_backstage_pass_very_close_to_sell_date_lower_bound_at_max_quality
def test_backstage_pass_on_sell_date
def test_backstage_pass_after_sell_date
Friday, March 7, 14

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@sandimetz Mar 2014
brie
Friday, March 7, 14

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@sandimetz Mar 2014
brie
sulfuras
Friday, March 7, 14

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@sandimetz Mar 2014
brie
sulfuras
backstage pass
Friday, March 7, 14

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@sandimetz Mar 2014
brie
sulfuras
backstage pass
normal
Friday, March 7, 14

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@sandimetz Mar 2014
item = GildedRose.new('normal', 10, 5)
item.tick
assert_equal 9, item.quality
assert_equal 4, item.days_remaining
end
let’s look at a test
Friday, March 7, 14

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@sandimetz Mar 2014
item.tick
end
Friday, March 7, 14

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@sandimetz Mar 2014
item.tick
end
name
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@sandimetz Mar 2014
item.tick
end
name
quality
Friday, March 7, 14

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@sandimetz Mar 2014
item.tick
end
name
quality
days_remaining
Friday, March 7, 14

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@sandimetz Mar 2014
item.tick
end
Friday, March 7, 14

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@sandimetz Mar 2014
item.tick
end
reduced by 1
Friday, March 7, 14

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@sandimetz Mar 2014
def test_conjured_item_before_sell_date
def test_conjured_item_at_zero_quality
def test_conjured_item_on_sell_date
def test_conjured_item_on_sell_date_at_zero_quality
def test_conjured_item_after_sell_date
def test_conjured_item_after_sell_date_at_zero_quality
end
Friday, March 7, 14

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@sandimetz Mar 2014
end
6 skipped tests
Friday, March 7, 14

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@sandimetz Mar 2014
end
Friday, March 7, 14

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@sandimetz Mar 2014
Friday, March 7, 14

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@sandimetz Mar 2014
Task:
Friday, March 7, 14

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@sandimetz Mar 2014
Task:
Implement Conjured
Friday, March 7, 14

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@sandimetz Mar 2014
end
Friday, March 7, 14

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@sandimetz Mar 2014
end
I tried
Friday, March 7, 14

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@sandimetz Mar 2014
end
but failed
Friday, March 7, 14

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@sandimetz Mar 2014
end
miserably
Friday, March 7, 14

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@sandimetz Mar 2014
the pattern failed me
Friday, March 7, 14

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@sandimetz Mar 2014
Friday, March 7, 14

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@sandimetz Mar 2014
Task:
Friday, March 7, 14

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@sandimetz Mar 2014
Task:
Refactor code so I can
Implement Conjured
Friday, March 7, 14

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@sandimetz Mar 2014
normal
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
# ....
def tick
if quality > 0
@quality -‐= 1
end
end
else
if quality < 50
@quality += 1
if quality < 50
@quality += 1
end
end
if quality < 50
@quality += 1
end
end
end
end
end
end
if quality > 0
@quality -‐= 1
end
end
else
end
else
if quality < 50
@quality += 1
end
end
end
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
def tick
if name == 'normal'
return
end
if quality > 0
@quality -‐= 1
end
end
else
if quality < 50
@quality += 1
if quality < 50
@quality += 1
end
end
if quality < 50
@quality += 1
end
end
end
end
end
end
if quality > 0
@quality -‐= 1
end
end
else
end
else
if quality < 50
@quality += 1
end
end
end
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if name == 'normal'
return
end
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
def tick
if name == 'normal'
return
end
if quality > 0
@quality -‐= 1
end
end
else
if quality < 50
@quality += 1
if quality < 50
@quality += 1
end
end
if quality < 50
@quality += 1
end
end
end
end
end
end
if quality > 0
@quality -‐= 1
end
end
else
end
else
if quality < 50
@quality += 1
end
end
end
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
# Running:
.S...S...S..SFF....F.....SS.F..
1) Failure:
GildedRoseTest#test_normal_item_of_zero_quality [gilded_rose_test.rb:37]:
Expected: 4
Actual: 5
2) Failure:
GildedRoseTest#test_normal_item_before_sell_date [gilded_rose_test.rb:12]:
Expected: 9
Actual: 10
3) Failure:
GildedRoseTest#test_normal_item_on_sell_date [gilded_rose_test.rb:20]:
Expected: 8
Actual: 10
4) Failure:
GildedRoseTest#test_normal_item_after_sell_date [gilded_rose_test.rb:28]:
Expected: 8
Actual: 10
Friday, March 7, 14

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@sandimetz Mar 2014
# Running:
.S...S...S..SFF....F.....SS.F..
1) Failure:
Expected: 4
Actual: 5
2) Failure:
Expected: 9
Actual: 10
3) Failure:
Expected: 8
Actual: 10
4) Failure:
Expected: 8
Actual: 10
4 failures
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def tick
if name == 'normal'
return
end
if @quality > 0
# ... 40 more lines
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def tick
if name == 'normal'
return
end
if @quality > 0
# ... 40 more lines
end
def normal_tick
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def tick
if name == 'normal'
return normal_tick
end
if @quality > 0
# ... 40 more lines
end
def normal_tick
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
# Running:
.S...S...S..SFF....F.....SS.F..
1) Failure:
Expected: 4
Actual: 5
2) Failure:
Expected: 9
Actual: 10
3) Failure:
Expected: 8
Actual: 10
4) Failure:
Expected: 8
Actual: 10
4 failures
Friday, March 7, 14

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@sandimetz Mar 2014
item.tick
end
Friday, March 7, 14

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@sandimetz Mar 2014
item.tick
end
class GildedRose
# ...
def normal_tick
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
item.tick
end
class GildedRose
# ...
def normal_tick
@quality -‐= 1
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
# Running:
.....S...FS....FS.S...FS....S..
1) Failure:
Expected: 0
Actual: -‐1
2) Failure:
Expected: 8
Actual: 9
3) Failure:
Expected: 8
Actual: 9
3 failures
Friday, March 7, 14

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@sandimetz Mar 2014
item.tick
assert_equal -‐1, item.days_remaining
end
class GildedRose
# ...
def normal_tick
@quality -‐= 1
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
item.tick
end
class GildedRose
# ...
def normal_tick
if @days_remaining > 0
@quality -‐= 1
end
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
item.tick
end
class GildedRose
# ...
def normal_tick
@quality -‐= 1
end
if @days_remaining <= 0
@quality -‐= 2
end
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
# Running:
...S.S.....S..S..SF.....S......
1) Failure:
Expected: 0
Actual: -‐1
1 failure ??
Friday, March 7, 14

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@sandimetz Mar 2014
item.tick
end
class GildedRose
# ...
def normal_tick
@quality -‐= 1
end
@quality -‐= 2
end
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
item.tick
end
class GildedRose
# ...
def normal_tick
if @quality != 0
@quality -‐= 1
end
@quality -‐= 2
end
end
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
# Running:
S..S.S...S..........S....S.....
Friday, March 7, 14

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@sandimetz Mar 2014
refactor under green
Friday, March 7, 14

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@sandimetz Mar 2014
def normal_tick
if @quality != 0
@quality -‐= 1
end
@quality -‐= 2
end
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
def normal_tick
end
def normal_tick
if @quality != 0
@quality -‐= 1
end
@quality -‐= 2
end
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
def normal_tick
return if @quality == 0
end
def normal_tick
if @quality != 0
@quality -‐= 1
end
@quality -‐= 2
end
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
def normal_tick
end
def normal_tick
@quality -‐= 1
end
@quality -‐= 2
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
def normal_tick
@quality -‐= 1
end
def normal_tick
@quality -‐= 1
end
@quality -‐= 2
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
def normal_tick
@quality -‐= 1
@quality -‐= 1 if @days_remaining <= 0
end
def normal_tick
@quality -‐= 1
end
@quality -‐= 2
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
def normal_tick
@quality -‐= 1
end
def normal_tick
end
Friday, March 7, 14

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@sandimetz Mar 2014
def normal_tick
@quality -‐= 1
end
Friday, March 7, 14

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@sandimetz Mar 2014
# Running:
S..S.S...S..........S....S.....
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def tick
if name == 'normal'
return normal_tick
end
if @quality > 0
# ... 40 more lines
end
end
Reprise
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def tick
if name == 'normal'
return normal_tick
end
if @quality > 0
# ... 40 more lines
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def tick
if name == 'normal'
return normal_tick
end
if @quality > 0
# ... 40 more lines
end
def normal_tick
@quality -‐= 1
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def tick
if name == 'normal'
return normal_tick
end
if @quality > 0
# ... 40 more lines
end
def normal_tick
@quality -‐= 1
end
end
normal
Friday, March 7, 14

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@sandimetz Mar 2014
# def test_normal ... etc
# def test_sulfuras ... etc
# def test_backstage ... etc
end
brie
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
if name == 'normal'
return normal_tick
end
# ...
end
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
case name
when 'normal'
return normal_tick
end
# ...
end
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
case name
when 'normal'
return normal_tick
when 'Aged Brie'
return brie_tick
end
# ...
end
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
case name
when 'normal'
return normal_tick
when 'Aged Brie'
return brie_tick
end
# ...
end
def brie_tick
end
Friday, March 7, 14

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@sandimetz Mar 2014
# Running:
.F...F.....S.S.F..S.FF.S.F.FS.S
1) Failure:
GildedRoseTest#test_brie_on_sell_date_with_max_quality [gilded_rose_test.rb:78]:
Expected: 4
Actual: 5
2) Failure:
GildedRoseTest#test_brie_on_sell_date_near_max_quality [gilded_rose_test.rb:69]:
Expected: 50
Actual: 49
3) Failure:
GildedRoseTest#test_brie_on_sell_date [gilded_rose_test.rb:61]:
Expected: 12
Actual: 10
4) Failure:
GildedRoseTest#test_brie_after_sell_date_with_max_quality [gilded_rose_test.rb:94]:
Expected: -‐11
Actual: -‐10
5) Failure:
GildedRoseTest#test_brie_before_sell_date_with_max_quality [gilded_rose_test.rb:54]:
Expected: 6
Actual: 7
7 failures
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
case name
when 'normal'
return normal_tick
when 'Aged Brie'
return brie_tick
end
# ...
end
def brie_tick
end
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
case name
when 'normal'
return normal_tick
when 'Aged Brie'
return brie_tick
end
# ...
end
def brie_tick
end
fast forward...
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
case name
when 'normal'
return normal_tick
when 'Aged Brie'
return brie_tick
end
# ...
end
def brie_tick
return if @quality >= 50
@quality += 1
@quality += 1 if @days_remaining <= 0
end
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
case name
when 'normal'
return normal_tick
when 'Aged Brie'
return brie_tick
end
# ...
end
def brie_tick
@quality += 1
end
brie
Friday, March 7, 14

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@sandimetz Mar 2014
# Running:
...S......S.....SS.....SS......
Friday, March 7, 14

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@sandimetz Mar 2014
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
Similarity
Friday, March 7, 14

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@sandimetz Mar 2014
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
Friday, March 7, 14

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@sandimetz Mar 2014
duplication is far cheaper
than the wrong abstraction
Friday, March 7, 14

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@sandimetz Mar 2014
# def test_brie ... etc
# def test_backstage ... etc
end
sulfuras
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
case name
when 'normal'
return normal_tick
when 'Aged Brie'
return brie_tick
when 'Sulfuras, Hand of Ragnaros'
return sulfuras_tick
end
# ...
end
def sulfuras_tick
end
Friday, March 7, 14

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@sandimetz Mar 2014
# Running:
...S......S.....SS.....SS......
0 failures ?!?
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
case name
when 'normal'
return normal_tick
when 'Aged Brie'
return brie_tick
end
# ...
end
def sulfuras_tick
end
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
case name
when 'normal'
return normal_tick
when 'Aged Brie'
return brie_tick
end
# ...
end
def sulfuras_tick
end
nothing changes
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
case name
when 'normal'
return normal_tick
when 'Aged Brie'
return brie_tick
end
# ...
end
def sulfuras_tick
end
sulfuras
Friday, March 7, 14

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@sandimetz Mar 2014
# def test_brie ... etc
# def test_sulfuras ... etc
end
backstage
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
case name
when 'normal'
when 'Aged Brie'
when 'Backstage passes to a TAFKAL80ETC concert'
return backstage_tick
end
# ...
end
def backstage_tick
return @quality = 0 if @days_remaining < 0
@quality += 1
@quality += 1 if @days_remaining < 10
end
backstage
Friday, March 7, 14

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@sandimetz Mar 2014
# Running:
...S......S.....SS.....SS......
Friday, March 7, 14

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@sandimetz Mar 2014
def tick
case name
when 'normal'
return normal_tick
when 'Aged Brie'
return brie_tick
end
# ...
end
def normal_tick
@quality -‐= 1
end
def brie_tick
def sulfuras_tick
def backstage_tick
class GildedRose
@name, @quality, @days_remaining = name, quality, days_remai
end
def tick
case name
when 'normal'
return normal_tick
when 'Aged Brie'
return brie_tick
end
if name != 'Aged Brie' && name != 'Backstage passes to a TAF
if quality > 0
@quality -‐= 1
end
end
else
if quality < 50
@quality += 1
if quality < 50
@quality += 1
end
end
if quality < 50
@quality += 1
end
end
end
end
end
end
if quality > 0
@quality -‐= 1
end
end
else
end
else
if quality < 50
@quality += 1
end
end
end
end
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
def sulfuras_tick
end
def backstage_tick
@quality += 1
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
# Running:
...S......S.....SS.....SS......
Friday, March 7, 14

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@sandimetz Mar 2014
small methods are simple
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
end
def tick
case name
when 'normal'
normal_tick
when 'Aged Brie'
brie_tick
sulfuras_tick
backstage_tick
end
end
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
def sulfuras_tick
end
def backstage_tick
@quality += 1
end
end
small methods
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
end
def tick
case name
when 'normal'
normal_tick
when 'Aged Brie'
brie_tick
sulfuras_tick
backstage_tick
end
end
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
def sulfuras_tick
end
def backstage_tick
@quality += 1
end
end
class GildedRose
end
def tick
if @name != 'Aged Brie' && @name != 'Backstage passes to a TAFKAL80ETC
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
end
big conditional small methods
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
end
def tick
case name
when 'normal'
normal_tick
when 'Aged Brie'
brie_tick
sulfuras_tick
backstage_tick
end
end
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
def sulfuras_tick
end
def backstage_tick
@quality += 1
end
end
0
25
50
big conditional
Total Complexity
50
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
end
def tick
case name
when 'normal'
normal_tick
when 'Aged Brie'
brie_tick
sulfuras_tick
backstage_tick
end
end
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
def sulfuras_tick
end
def backstage_tick
@quality += 1
end
end
0
25
50
tick normal brie backstage other
40
Total Complexity
50
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
end
def tick
case name
when 'normal'
normal_tick
when 'Aged Brie'
brie_tick
sulfuras_tick
backstage_tick
end
end
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
def sulfuras_tick
end
def backstage_tick
@quality += 1
end
end
0
25
50
tick normal brie backstage other
12
40
45
Total Complexity
50
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
end
def tick
case name
when 'normal'
normal_tick
when 'Aged Brie'
brie_tick
sulfuras_tick
backstage_tick
end
end
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
def sulfuras_tick
end
def backstage_tick
@quality += 1
end
end
Complexity
50
big conditional
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
end
def tick
case name
when 'normal'
normal_tick
when 'Aged Brie'
brie_tick
sulfuras_tick
backstage_tick
end
end
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
def sulfuras_tick
end
def backstage_tick
@quality += 1
end
end
0
45
90
Complexity
50
big conditional
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
end
def tick
case name
when 'normal'
normal_tick
when 'Aged Brie'
brie_tick
sulfuras_tick
backstage_tick
end
end
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
def sulfuras_tick
end
def backstage_tick
@quality += 1
end
end
0
45
90
Complexity
50
84
40
small methods
big conditional 10 Refactorings
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
Task:
Implement Conjured
Friday, March 7, 14

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@sandimetz Mar 2014
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
def sulfuras_tick
end
def backstage_tick
@quality += 1
end
Friday, March 7, 14

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@sandimetz Mar 2014
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
def sulfuras_tick
end
def backstage_tick
@quality += 1
end
def normal_tick
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
def sulfuras_tick
end
def backstage_tick
@quality += 1
end
def normal_tick
def brie_tick
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
def sulfuras_tick
end
def backstage_tick
@quality += 1
end
def normal_tick
def brie_tick
def sulfuras_tick
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
def sulfuras_tick
end
def backstage_tick
@quality += 1
end
def normal_tick
def brie_tick
def sulfuras_tick
def backstage_tick
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
def sulfuras_tick
end
def backstage_tick
@quality += 1
end
def normal_tick
def brie_tick
def sulfuras_tick
def backstage_tick
def conjured_tick
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
def sulfuras_tick
end
def backstage_tick
@quality += 1
end
def normal_tick
def brie_tick
def sulfuras_tick
def backstage_tick
def conjured_tick
???
Friday, March 7, 14

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@sandimetz Mar 2014
the pattern still fails me
Friday, March 7, 14

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@sandimetz Mar 2014
open / closed
Friday, March 7, 14

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@sandimetz Mar 2014
open for extension
Friday, March 7, 14

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@sandimetz Mar 2014
open for extension
closed for modiﬁcation
Friday, March 7, 14

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@sandimetz Mar 2014
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
def sulfuras_tick
end
def backstage_tick
@quality += 1
end
def normal_tick
def brie_tick
def sulfuras_tick
def backstage_tick
Friday, March 7, 14

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@sandimetz Mar 2014
they’re screaming to get out
Friday, March 7, 14

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@sandimetz Mar 2014
GildedRose
Friday, March 7, 14

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@sandimetz Mar 2014
brie_tick
backstage_tick
sulfuras_tick
normal_tick
GildedRose
Friday, March 7, 14

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@sandimetz Mar 2014
Normal
brie_tick
backstage_tick
sulfuras_tick
normal_tick
GildedRose
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
tick
Normal
brie_tick
backstage_tick
sulfuras_tick
normal_tick
GildedRose
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
tick
Normal
brie_tick
backstage_tick
sulfuras_tick
GildedRose
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
tick
Normal
GildedRose
brie_tick
backstage_tick
sulfuras_tick
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
def normal_tick
@quality -‐= 1
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
def tick
@quality -‐= 1
end
Friday, March 7, 14

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@sandimetz Mar 2014
class Normal
def tick
@quality -‐= 1
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
class Normal
def initialize(quality, days_remaining)
@quality, @days_remaining = quality, days_remaining
end
def tick
@quality -‐= 1
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
class Normal
attr_reader :quality, :days_remaining
end
def tick
@quality -‐= 1
end
end
Friday, March 7, 14

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@sandimetz Mar 2014

class Normal
end
def tick
@quality -‐= 1
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def normal_tick
end
class Normal
end
def tick
@quality -‐= 1
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def normal_tick
@item = Normal.new(quality, days_remaining)
end
class Normal
end
def tick
@quality -‐= 1
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def normal_tick
item.tick
end
class Normal
end
def tick
@quality -‐= 1
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
tick
Normal
GildedRose
brie_tick
backstage_tick
sulfuras_tick
Friday, March 7, 14

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@sandimetz Mar 2014
normal is an object
Friday, March 7, 14

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@sandimetz Mar 2014
brie/sulfuras/backstage are not
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def normal_tick
item.tick
end
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def normal_tick
item.tick
end
def brie_tick
@quality += 1
end
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def normal_tick
item.tick
end
def brie_tick
@quality += 1
end
def quality
end
def days_remaining
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
def normal_tick
item.tick
end
def brie_tick
@quality += 1
end
def quality
return item.quality if item
end
def days_remaining
end
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def normal_tick
item.tick
end
def brie_tick
@quality += 1
end
def quality
@quality
end
def days_remaining
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
def normal_tick
item.tick
end
def brie_tick
@quality += 1
end
def quality
@quality
end
def days_remaining
return item.days_remaining if item
@days_remaining
end
Friday, March 7, 14

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@sandimetz Mar 2014
brie
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def brie_tick
@quality += 1
end
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def brie_tick
@quality += 1
end
class Brie
end
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def brie_tick
@quality += 1
end
class Brie
def tick
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
def brie_tick
end
class Brie
def tick
@quality += 1
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
def brie_tick
end
class Brie
end
def tick
@quality += 1
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def brie_tick
@item = Brie.new(quality, days_remaining)
item.tick
end
class Brie
end
def tick
@quality += 1
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
sulfuras
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def sulfuras_tick
end
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def sulfuras_tick
end
class Sulfuras
end
def tick
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def sulfuras_tick
@item = Sulfuras.new(quality, days_remaining)
item.tick
end
class Sulfuras
end
def tick
end
end
Friday, March 7, 14

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@sandimetz Mar 2014
backstage
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def backstage_tick
@quality += 1
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
def backstage_tick
@quality += 1
end
class Backstage
def tick
end
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def backstage_tick
end
class Backstage
def tick
@quality += 1
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
def backstage_tick
end
class Backstage
end
def tick
@quality += 1
end
Friday, March 7, 14

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@sandimetz Mar 2014
class GildedRose
def backstage_tick
@item = Backstage.new(quality, days_remaining)
item.tick
end
class Backstage
end
def tick
@quality += 1
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
normal/brie/sulfuras/backstage
are now objects
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
GildedRose
tick
Normal
tick
Brie
tick
Sulfuras
attr_reader :item
tick
Backstage
attr_reader
:quality,
:days_remaining
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
def tick
case name
when 'normal'
normal_tick
when 'Aged Brie'
brie_tick
sulfuras_tick
backstage_tick
end
end
def normal_tick
item.tick
end
def brie_tick
item.tick
end
# etc
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
rewind
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
def tick
case name
when 'normal'
normal_tick
when 'Aged Brie'
brie_tick
sulfuras_tick
backstage_tick
end
end
def normal_tick
item.tick
end
def brie_tick
item.tick
end
# etc
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
def tick
case name
when 'normal'
when 'Aged Brie'
brie_tick
sulfuras_tick
backstage_tick
end
end
def normal_tick
item.tick
end
def brie_tick
item.tick
end
# etc
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
def tick
case name
when 'normal'
item.tick
when 'Aged Brie'
brie_tick
sulfuras_tick
backstage_tick
end
end
def normal_tick
end
def brie_tick
item.tick
end
# etc
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
def tick
case name
when 'normal'
item.tick
when 'Aged Brie'
brie_tick
sulfuras_tick
backstage_tick
end
end
def brie_tick
item.tick
end
# etc
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
def tick
case name
when 'normal'
item.tick
when 'Aged Brie'
end
end
def brie_tick
item.tick
end
# etc
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
def tick
case name
when 'normal'
item.tick
when 'Aged Brie'
item.tick
item.tick
item.tick
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
abstract away the duplication
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
def tick
case name
when 'normal'
item.tick
when 'Aged Brie'
item.tick
item.tick
item.tick
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
attr_reader :name, :item
end
def tick
case name
when 'normal'
item.tick
when 'Aged Brie'
item.tick
item.tick
item.tick
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
@item = ???
end
def tick
case name
when 'normal'
item.tick
when 'Aged Brie'
item.tick
item.tick
item.tick
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
@item = ???.new(quality, days_remaining)
end
def tick
case name
when 'normal'
item.tick
when 'Aged Brie'
item.tick
item.tick
item.tick
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
end
def
case name
when 'normal'
Normal
when 'Aged Brie'
Brie
Sulfuras
Backstage
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
end
def
case name
when 'normal'
Normal
when 'Aged Brie'
Brie
Sulfuras
Backstage
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
end
def klass_for(name)
case name
when 'normal'
Normal
when 'Aged Brie'
Brie
Sulfuras
Backstage
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
@item = klass_for(name).new(quality, days_remaining)
end
def klass_for(name)
case name
when 'normal'
Normal
when 'Aged Brie'
Brie
Sulfuras
Backstage
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
attr_reader :item
end
def klass_for(name)
case name
when 'normal'
Normal
when 'Aged Brie'
Brie
Sulfuras
Backstage
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
attr_reader :item
end
def klass_for(name)
# ...
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
attr_reader :item
end
def klass_for(name)
# ...
end
def tick
item.tick
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
attr_reader :item
end
def klass_for(name)
# ...
end
def tick
item.tick
end
def quality
@quality
end
def days_remaining
@days_remaining
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
attr_reader :item
end
def klass_for(name)
# ...
end
def tick
item.tick
end
def quality
end
def days_remaining
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
attr_reader :item
end
def klass_for(name)
# ...
end
def tick
item.tick
end
def quality
item.quality
end
def days_remaining
item.days_remaining
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
attr_reader :item
end
def klass_for(name)
# ...
end
def tick
item.tick
end
def quality
item.quality
end
def days_remaining
item.days_remaining
end
class Normal
class Brie
class Sulfuras
class Backstage
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
item is a role
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
GildedRose
tick
Normal
tick
Brie
tick
Sulfuras
attr_reader :item
tick
Backstage
attr_reader
:quality,
:days_remaining
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
attr_reader :item
GildedRose
ItemRole
def tick
def quality
def days_remaining
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
attr_reader :item
ItemRole
def tick
def quality
def days_remaining
GildedRose
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
attr_reader :item
def tick
end
def quality
end
def days_remaining
end
ItemRole
def tick
def quality
def days_remaining
GildedRose
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
attr_reader :item
def tick
item.tick
end
def quality
item.quality
end
def days_remaining
item.days_remaining
end
GildedRose
ItemRole
def tick
def quality
def days_remaining
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
Foo
def tick
item.tick
end
def quality
item.quality
end
def days_remaining
item.days_remaining
end
attr_reader :item
GildedRose
ItemRole
def tick
def quality
def days_remaining
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
Foo
def tick
item.tick
end
def quality
item.quality
end
def days_remaining
item.days_remaining
end
attr_reader :item
attr_reader :rose
GildedRose
ItemRole
def tick
def quality
def days_remaining
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
Foo
def tick
item.tick
end
def quality
item.quality
end
def days_remaining
item.days_remaining
end
attr_reader :item
attr_reader :rose
def doit
rose.tick
rose.quality
rose.days_remaining
end
GildedRose
ItemRole
def tick
def quality
def days_remaining
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
Foo
def tick
item.tick
end
def quality
item.quality
end
def days_remaining
item.days_remaining
end
attr_reader :item
attr_reader :rose
def doit
rose.tick
rose.quality
rose.days_remaining
end
GildedRose
ItemRole
def tick
def quality
def days_remaining
Middleman
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
Foo
attr_reader :item
attr_reader :rose
GildedRose
ItemRole
def tick
def quality
def days_remaining
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
Foo
attr_reader :item
attr_reader :rose
def getit
@rose =
GildedRose.new(
‘normal’, ...)
end
GildedRose
ItemRole
def tick
def quality
def days_remaining
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
Foo
def initialize(name,...)
@item =
klass_for(name).
new(
quality,
days_remaining)
end
def klass_for(name)
case name
when 'normal'
Normal
attr_reader :item
attr_reader :rose
def getit
@rose =
GildedRose.new(
‘normal’, ...)
end
GildedRose
ItemRole
def tick
def quality
def days_remaining
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
Foo
def initialize(name,...)
@item =
klass_for(name).
new(
quality,
days_remaining)
end
def klass_for(name)
case name
when 'normal'
Normal
attr_reader :item
attr_reader :rose
def getit
@rose =
GildedRose.new(
‘normal’, ...)
end
GildedRose
ItemRole
def tick
def quality
def days_remaining
Item
Factory
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
attr_reader :item
end
def klass_for(name)
# ...
end
def tick
item.tick
end
def quality
item.quality
end
def days_remaining
item.days_remaining
end
class Normal
class Brie
class Sulfuras
class Backstage
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
attr_reader :item
end
def klass_for(name)
# ...
end
def tick
item.tick
end
def quality
item.quality
end
def days_remaining
item.days_remaining
end
class Normal
class Brie
class Sulfuras
class Backstage
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
attr_reader :item
def self.for(name, quality, days_remaining)
end
def klass_for(name)
# ...
end
def tick
item.tick
end
def quality
item.quality
end
def days_remaining
item.days_remaining
end
class Normal
class Brie
class Sulfuras
class Backstage
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
attr_reader :item
end
def self.klass_for(name)
# ...
end
def tick
item.tick
end
def quality
item.quality
end
def days_remaining
item.days_remaining
end
class Normal
class Brie
class Sulfuras
class Backstage
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
attr_reader :item
klass_for(name).new(quality, days_remaining)
end
# ...
end
def tick
item.tick
end
def quality
item.quality
end
def days_remaining
item.days_remaining
end
class Normal
class Brie
class Sulfuras
class Backstage
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
end
# ...
end
def tick
item.tick
end
def quality
item.quality
end
def days_remaining
item.days_remaining
end
class Normal
class Brie
class Sulfuras
class Backstage
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
end
# ...
end
def tick
item.tick
end
def quality
item.quality
end
def days_remaining
item.days_remaining
end
class Normal
class Brie
class Sulfuras
class Backstage
end
Middleman
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
end
# ...
end
class Normal
class Brie
class Sulfuras
class Backstage
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
Foo
def self.for(name,...)
end
attr_reader :rose
def getit
@rose =
GildedRose.for(
‘normal’, ...)
end
GildedRose
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
Foo
attr_reader :rose
def getit
@rose =
GildedRose.for(
‘normal’, ...)
end
ItemRole
def tick
def quality
def days_remaining
def self.for(name,...)
end
GildedRose
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
extract common code
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
end
# ...
end
class Normal
class Brie
class Sulfuras
class Backstage
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Normal
end
def tick
# ...
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Normal
end
def tick
# ...
end
end
class Brie
end
def tick
# ...
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Normal
end
def tick
# ...
end
end
class Brie
end
def tick
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
class Normal
end
def tick
# ...
end
end
class Brie
end
def tick
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
end
class Normal
def tick
# ...
end
end
class Brie
end
def tick
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
end
class Normal < Item
def tick
# ...
end
end
class Brie
end
def tick
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
end
class Normal < Item
def tick
# ...
end
end
class Brie
end
def tick
# ...
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
end
class Normal < Item
def tick
# ...
end
end
class Brie < Item
end
def tick
# ...
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
end
class Normal < Item
def tick
# ...
end
end
class Brie < Item
def tick
# ...
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
end
class Normal < Item
def tick
# ...
end
end
class Brie < Item
def tick
# ...
end
end
class Sulfuras < Item
def tick
end
end
class Backstage < Item
def tick
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
inheritance is not evil
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
but programmers sometimes are
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
end
class Normal < Item
def tick
# ...
end
end
class Brie < Item
def tick
# ...
end
end
def tick
end
end
def tick
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
end
class Normal < Item
def tick
# ...
end
end
class Brie < Item
def tick
# ...
end
end
def tick
end
end
def tick
Item
quality
days_remaining
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
end
class Normal < Item
def tick
# ...
end
end
class Brie < Item
def tick
# ...
end
end
def tick
end
end
def tick
Item
quality
days_remaining
Normal
Brie
Sulfuras
Backstage
quality
days_remaining
tick
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
end
class Normal < Item
def tick
# ...
end
end
class Brie < Item
def tick
# ...
end
end
def tick
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
def tick
end
end
class Normal < Item
def tick
# ...
end
end
class Brie < Item
def tick
# ...
end
end
def tick
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
def tick
end
end
def tick
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
def tick
end
end
def tick
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
def tick
end
end
def tick
end
end
case name
when 'normal'
Normal
when 'Aged Brie'
Brie
Sulfuras
Backstage
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
def tick
end
end
def tick
end
end
case name
when 'normal'
Normal
when 'Aged Brie'
Brie
Item
Backstage
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
def tick
end
end
case name
when 'normal'
Normal
when 'Aged Brie'
Brie
Item
Backstage
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
extract conﬁguration
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
end
case name
when 'normal'
Normal
when 'Aged Brie'
Brie
Item
Backstage
end
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
DEFAULT_CLASS = Item
SPECIALIZED_CLASSES = {
'normal' => Normal,
'Aged Brie' => Brie,
'Backstage passes to a TAFKAL80ETC concert' => Backstage }
end
case name
when 'normal'
Normal
when 'Aged Brie'
Brie
Item
Backstage
end
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
'normal' => Normal,
klass_for(name).
new(quality, days_remaining)
end
case name
when 'normal'
Normal
when 'Aged Brie'
Brie
Item
Backstage
end
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
'normal' => Normal,
(SPECIALIZED_CLASSES[name] || DEFAULT_CLASS).
end
case name
when 'normal'
Normal
when 'Aged Brie'
Brie
Item
Backstage
end
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
'normal' => Normal,
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
small objects
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
def tick
end
end
class Normal < Item
def tick
@quality -‐= 1
end
end
module GildedRose
class Item
end
def tick
end
end
class Normal < Item
def tick
@quality -‐= 1
end
end
class Brie < Item
def tick
@quality += 1
end
end
def tick
@quality += 1
end
end
'normal' => Normal,
(SPECIALIZED_CLASSES[name] || DEFAULT_CLASS).new(quality,
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Brie < Item
def tick
@quality += 1
end
end
def tick
@quality += 1
end
end
module GildedRose
class Item
end
def tick
end
end
class Normal < Item
def tick
@quality -‐= 1
end
end
class Brie < Item
def tick
@quality += 1
end
end
def tick
@quality += 1
end
end
'normal' => Normal,
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
'normal' => Normal,
end
end module GildedRose
class Item
end
def tick
end
end
class Normal < Item
def tick
@quality -‐= 1
end
end
class Brie < Item
def tick
@quality += 1
end
end
def tick
@quality += 1
end
end
'normal' => Normal,
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
def tick
end
end
class Normal < Item
def tick
@quality -‐= 1
end
end
class Brie < Item
def tick
@quality += 1
end
end
def tick
@quality += 1
end
end
'normal' => Normal,
(SPECIALIZED_CLASSES[name] || DEFAULT_CLASS).new(quality, days_remainin
end
end small objects
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
def tick
end
end
class Normal < Item
def tick
@quality -‐= 1
end
end
class Brie < Item
def tick
@quality += 1
end
end
def tick
@quality += 1
end
end
'normal' => Normal,
end
end small objects
class GildedRose
end
def tick
if @name != 'Aged Brie' && @name != 'Backstage passes to a TAFKAL80ETC
if @quality > 0
@quality -‐= 1
end
end
else
if @quality < 50
@quality += 1
if @quality < 50
@quality += 1
end
end
if @quality < 50
@quality += 1
end
end
end
end
end
end
if @quality > 0
@quality -‐= 1
end
end
else
end
else
if @quality < 50
@quality += 1
end
end
end
end
end
big conditional
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
def tick
end
end
class Normal < Item
def tick
@quality -‐= 1
end
end
class Brie < Item
def tick
@quality += 1
end
end
def tick
@quality += 1
end
end
'normal' => Normal,
end
end
small methods
class GildedRose
end
def tick
case name
when 'normal'
normal_tick
when 'Aged Brie'
brie_tick
sulfuras_tick
backstage_tick
end
end
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
def sulfuras_tick
end
def backstage_tick
@quality += 1
end
end
small objects
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
def tick
end
end
class Normal < Item
def tick
@quality -‐= 1
end
end
class Brie < Item
def tick
@quality += 1
end
end
def tick
@quality += 1
end
end
'normal' => Normal,
(SPECIALIZED_CLASSES[name] || DEFAULT_CLASS).new(quality, days_remaining)
end
end
0
25
50
big conditional small methods small objects
tick/for normal brie backstage other
Total Complexity
40
50
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
def tick
end
end
class Normal < Item
def tick
@quality -‐= 1
end
end
class Brie < Item
def tick
@quality += 1
end
end
def tick
@quality += 1
end
end
'normal' => Normal,
end
end
0
25
50
33
40
50
Total Complexity
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
end
def tick
case name
when 'normal'
normal_tick
when 'Aged Brie'
brie_tick
sulfuras_tick
backstage_tick
end
end
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
def sulfuras_tick
end
def backstage_tick
@quality += 1
end
end
50
84
40
Total Complexity
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
end
def tick
case name
when 'normal'
normal_tick
when 'Aged Brie'
brie_tick
sulfuras_tick
backstage_tick
end
end
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
def sulfuras_tick
end
def backstage_tick
@quality += 1
end
end
0
45
90
50
84
40
Total Complexity
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
class GildedRose
end
def tick
case name
when 'normal'
normal_tick
when 'Aged Brie'
brie_tick
sulfuras_tick
backstage_tick
end
end
def normal_tick
@quality -‐= 1
end
def brie_tick
@quality += 1
end
def sulfuras_tick
end
def backstage_tick
@quality += 1
end
end
0
45
90
50
84
40 33
86
Total Complexity
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
def tick
end
end
class Normal < Item
def tick
@quality -‐= 1
end
end
class Brie < Item
def tick
@quality += 1
end
end
def tick
@quality += 1
end
end
'normal' => Normal,
end
end
0
25
50
big cond small meth small objs
33
Complexity
40
50
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
def tick
end
end
class Normal < Item
def tick
@quality -‐= 1
end
end
class Brie < Item
def tick
@quality += 1
end
end
def tick
@quality += 1
end
end
'normal' => Normal,
end
end
0
25
50
GildedRose small meth small objs
33
Complexity
40
50
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
def tick
end
end
class Normal < Item
def tick
@quality -‐= 1
end
end
class Brie < Item
def tick
@quality += 1
end
end
def tick
@quality += 1
end
end
'normal' => Normal,
end
end
0
25
50
GildedRose GildedRose(2) small objs
33
Complexity
40
50
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
def tick
end
end
class Normal < Item
def tick
@quality -‐= 1
end
end
class Brie < Item
def tick
@quality += 1
end
end
def tick
@quality += 1
end
end
'normal' => Normal,
end
end
0
25
50
GildedRose GildedRose(2) many objs
33
Complexity
40
50
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
def tick
end
end
class Normal < Item
def tick
@quality -‐= 1
end
end
class Brie < Item
def tick
@quality += 1
end
end
def tick
@quality += 1
end
end
'normal' => Normal,
end
end
0
25
50
GildedRose GildedRose(2) many objs Backstage
33
Complexity
40
50
12
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
def tick
end
end
class Normal < Item
def tick
@quality -‐= 1
end
end
class Brie < Item
def tick
@quality += 1
end
end
def tick
@quality += 1
end
end
'normal' => Normal,
end
end
0
25
50
GildedRose GildedRose(2) many objs Backstage average
33
Complexity
40
50
7
12
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
def tick
end
end
class Normal < Item
def tick
@quality -‐= 1
end
end
class Brie < Item
def tick
@quality += 1
end
end
def tick
@quality += 1
end
end
'normal' => Normal,
end
end
0
25
50
GildedRose Backstage
Complexity
50
12
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Item
end
def tick
end
end
class Normal < Item
def tick
@quality -‐= 1
end
end
class Brie < Item
def tick
@quality += 1
end
end
def tick
@quality += 1
end
end
'normal' => Normal,
end
end
0
25
50
GildedRose Backstage
Complexity
50
12
75%
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
Task:
Implement Conjured
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
class Conjured < Item
def tick
@quality -‐= 2
end
end
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
def tick
@quality -‐= 2
end
end
'normal' => Normal,
'Backstage passes to a TAFKAL80ETC concert' => Backstage}
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
module GildedRose
def tick
@quality -‐= 2
end
end
'normal' => Normal,
'Backstage passes to a TAFKAL80ETC concert' => Backstage,
'Conjured Mana Cake' => Conjured }
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
# Running:
...............................
Friday, March 7, 14

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@sandimetz Mar 2014
Summary
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
duplication is far cheaper
than the wrong abstraction
Friday, March 7, 14

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@sandimetz Mar 2014
reach for open / closed
Friday, March 7, 14

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@sandimetz Mar 2014
small methods are simple
Friday, March 7, 14

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@sandimetz Mar 2014
small objects are simple
Friday, March 7, 14

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@sandimetz Mar 2014
refactor through complexity
Friday, March 7, 14

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@sandimetz Mar 2014
refactor into simplicity
Friday, March 7, 14

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@sandimetz Mar 2014
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
Thanks
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
Thanks
Jim
Friday, March 7, 14

View Slide

@sandimetz Mar 2014
Questions?
Friday, March 7, 14

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http://poodr.com
Sandi Metz
@sandimetz
@sandimetz Mar 2014
Friday, March 7, 14

View Slide

all the little things (rubyonales)

all the little things (rubyonales)

Sandi Metz

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