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Alan Ridlehoover & Fito von Zastrow
RubyConf Mini 2022
The Coffee
Machine Talk
A Brewer’s Guide to Filtering out
Complexity and Churn
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PRONOUNS
he/him/his
HOMETOWN
Asunción
RUBY EXPERIENCE
12 years
FAVORITE COFFEE
Ghirardelli Dark
Chocolate Mocha
PRONOUNS
he/him/his
HOMETOWN
Seattle
RUBY EXPERIENCE
12 years
FAVORITE COFFEE
New Orleans Cold
Brew w/ Chicory
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No content
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🤲
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No content
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No content
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👍
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How did we get here?
How complexity sneaks into a code base.
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☕ Story: As a patron, I want coffee
class CoffeeMachine
def vend
dispense_cup
heat_water
prepare_grounds
dispense_water
dispose_of_grounds
end
end
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☕ Story: As a patron, I want tea
class CoffeeMachine
def vend(drink: :coffee)
if drink == :coffee
dispense_cup
heat_water
prepare_grounds
dispense_water
dispose_of_grounds
elsif drink == :tea
dispense_cup
dispense_tea_bag
heat_water
dispense_water
end
end
end
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☕ Refactor: DRY up the code
class CoffeeMachine
def vend(drink: :coffee)
dispense_cup
heat_water
if drink == :coffee
prepare_grounds
elsif drink == :tea
dispense_tea_bag
end
dispense_water
dispose_of_grounds if drink == :coffee
end
end
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☕ Story: As a patron, I want sweetener
class CoffeeMachine
def vend(drink: :coffee, options: {})
dispense_cup
heat_water
if drink == :coffee
prepare_grounds
elsif drink == :tea
dispense_tea_bag
end
dispense_water
dispense_sweetener if options[:sweet]
dispose_of_grounds if drink == :coffee
end
end
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☕ Story: As a patron, I want cream
class CoffeeMachine
def vend(drink: :coffee, options: {})
dispense_cup
heat_water
if drink == :coffee
prepare_grounds
elsif drink == :tea
dispense_tea_bag
end
dispense_water
dispense_sweetener if options[:sweet]
dispense_cream if options[:creamy]
dispose_of_grounds if drink == :coffee
end
end
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☕ Story: As a patron, I want cocoa
class CoffeeMachine
def vend(drink: :coffee, options: {})
dispense_cup
heat_water
if drink == :coffee
prepare_grounds
elsif drink == :tea
dispense_tea_bag
elsif drink == :cocoa
dispense_cocoa_mix
end
dispense_water
unless drink == :cocoa
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
end
dispose_of_grounds if drink == :coffee
end
end
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☕ Story: As a patron, I want whipped cream
class CoffeeMachine
def vend(drink: :coffee, options: {})
dispense_cup
heat_water
if drink == :coffee
prepare_grounds
elsif drink == :tea
dispense_tea_bag
elsif drink == :cocoa
dispense_cocoa_mix
end
dispense_water
unless drink == :cocoa
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
end
unless drink == :tea
dispense_whipped_cream if options[:fluffy]
end
dispose_of_grounds if drink == :coffee
end
end
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Do you smell that?
How to recognize the problem before it
becomes painful and frustrating.
Rules by Sandi Metz Flog by Ryan Davis
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☕ Measuring complexity with the flog gem
Score of Means
- - - - - - - - - - - - - - - - - - - - - - - - -
0-10 Awesome
11-20 Good enough
21-40 Might need refactoring
41-60 Possible to justify
61-100 Danger
100-200 Whoop, whoop, whoop
200 + Someone please think of the children
(note: these are scores for an individual method)
What's a good
fl
og score? by Jake Scruggs
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☕ Story: As a patron, I want coffee
class CoffeeMachine
def vend
dispense_cup
heat_water
prepare_grounds
dispense_water
dispose_of_grounds
end
end
Churn
1
Complexity
5.5
10
20
30
25
15
5
0
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☕ Story: As a patron, I want tea
class CoffeeMachine
def vend(drink: :coffee)
if drink == :coffee
dispense_cup
heat_water
prepare_grounds
dispense_water
dispose_of_grounds
elsif drink == :tea
dispense_cup
dispense_tea_bag
heat_water
dispense_water
end
end
end
Churn
2
Complexity
14.6
10
20
30
25
15
5
0
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☕ Refactor: DRY up the code
class CoffeeMachine
def vend(drink: :coffee)
dispense_cup
heat_water
if drink == :coffee
prepare_grounds
elsif drink == :tea
dispense_tea_bag
end
dispense_water
dispose_of_grounds if drink == :coffee
end
end
Churn
3
Complexity
10.9
10
20
30
25
15
5
0
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☕ Story: As a patron, I want sweetener
class CoffeeMachine
def vend(drink: :coffee, options: {})
dispense_cup
heat_water
if drink == :coffee
prepare_grounds
elsif drink == :tea
dispense_tea_bag
end
dispense_water
dispense_sweetener if options[:sweet]
dispose_of_grounds if drink == :coffee
end
end
Churn
4
Complexity
13.5
10
20
30
25
15
5
0
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☕ Story: As a patron, I want cream
class CoffeeMachine
def vend(drink: :coffee, options: {})
dispense_cup
heat_water
if drink == :coffee
prepare_grounds
elsif drink == :tea
dispense_tea_bag
end
dispense_water
dispense_sweetener if options[:sweet]
dispense_cream if options[:creamy]
dispose_of_grounds if drink == :coffee
end
end
Churn
5
Complexity
16.0
10
20
30
25
15
5
0
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☕ Story: As a patron, I want cocoa
class CoffeeMachine
def vend(drink: :coffee, options: {})
dispense_cup
heat_water
if drink == :coffee
prepare_grounds
elsif drink == :tea
dispense_tea_bag
elsif drink == :cocoa
dispense_cocoa_mix
end
dispense_water
unless drink == :cocoa
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
end
dispose_of_grounds if drink == :coffee
end
end
Churn
6
Complexity
21.3
10
20
30
25
15
5
0
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☕ Story: As a patron, I want whipped cream
class CoffeeMachine
def vend(drink: :coffee, options: {})
dispense_cup
heat_water
if drink == :coffee
prepare_grounds
elsif drink == :tea
dispense_tea_bag
elsif drink == :cocoa
dispense_cocoa_mix
end
dispense_water
unless drink == :cocoa
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
end
unless drink == :tea
dispense_whipped_cream if options[:fluffy]
end
dispose_of_grounds if drink == :coffee
end
end
Churn
7
Complexity
25.5
10
20
30
25
15
5
0
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☕ CoffeeMachine Pain Index over time
class CoffeeMachine
def vend(drink: :coffee, options: {})
dispense_cup
heat_water
if drink == :coffee
prepare_grounds
elsif drink == :tea
dispense_tea_bag
elsif drink == :cocoa
dispense_cocoa_mix
end
dispense_water
unless drink == :cocoa
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
end
unless drink == :tea
dispense_whipped_cream if options[:fluffy]
end
dispose_of_grounds if drink == :coffee
end
end
Churn
7
Complexity
25.5
10
20
30
25
15
5
0
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☕ CoffeeMachine Pain Index over time
class CoffeeMachine
def vend(drink: :coffee, options: {})
dispense_cup
heat_water
if drink == :coffee
prepare_grounds
elsif drink == :tea
dispense_tea_bag
elsif drink == :cocoa
dispense_cocoa_mix
end
dispense_water
unless drink == :cocoa
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
end
unless drink == :tea
dispense_whipped_cream if options[:fluffy]
end
dispose_of_grounds if drink == :coffee
end
end
Churn
7
Complexity
25.5
10
20
30
25
15
5
0
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Can we turn it around?
How to
fi
lter out complexity and churn.
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☕ Refactor: Rehydrate to see missing abstractions
class CoffeeMachine
def vend(drink: :coffee, options: {})
dispense_cup
heat_water
if drink == :coffee
prepare_grounds
elsif drink == :tea
dispense_tea_bag
elsif drink == :cocoa
dispense_cocoa_mix
end
dispense_water
unless drink == :cocoa
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
end
unless drink == :tea
dispense_whipped_cream if options[:fluffy]
end
dispose_of_grounds if drink == :coffee
end
end
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☕ Refactor: Rehydrate to see missing abstractions
class CoffeeMachine
def vend(drink: :coffee, options: {})
if drink == :coffee
dispense_cup
heat_water
prepare_grounds
dispense_water
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
dispense_whipped_cream if options[:fluffy]
dispose_of_grounds
elsif drink == :tea
dispense_cup
heat_water
dispense_tea_bag
dispense_water
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
elsif drink == :cocoa
dispense_cup
heat_water
dispense_cocoa_mix
dispense_water
dispense_whipped_cream if options[:fluffy]
end
end
end
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☕ Refactor: Extract polymorphic objects
class CoffeeMachine
def vend(drink: :coffee, options: {})
if drink == :coffee
Coffee.new(options: options).prepare
elsif drink == :tea
Tea.new(options: options).prepare
elsif drink == :cocoa
Cocoa.new(options: options).prepare
end
end
end
class Coffee
def prepare
dispense_cup
heat_water
prepare_grounds
dispense_water
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
dispense_whipped_cream if options[:fluffy]
dispose_of_grounds
end
end
class Tea
def prepare
dispense_cup
heat_water
dispense_tea_bag
dispense_water
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
end
end
class Cocoa
def prepare
dispense_cup
heat_water
dispense_cocoa_mix
dispense_water
dispense_whipped_cream if options[:fluffy]
end
end
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☕ Refactor: Extract polymorphic objects
class CoffeeMachine
def vend(drink: :coffee, options: {})
if drink == :coffee
Coffee.new(options: options).prepare
elsif drink == :tea
Tea.new(options: options).prepare
elsif drink == :cocoa
Cocoa.new(options: options).prepare
end
end
end
class Coffee
def prepare
dispense_cup
heat_water
prepare_grounds
dispense_water
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
dispense_whipped_cream if options[:fluffy]
dispose_of_grounds
end
end
class Tea
def prepare
dispense_cup
heat_water
dispense_tea_bag
dispense_water
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
end
end
class Cocoa
def prepare
dispense_cup
heat_water
dispense_cocoa_mix
dispense_water
dispense_whipped_cream if options[:fluffy]
end
end
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☕ Refactor: Extract factory class
class CoffeeMachine
def vend(drink: :coffee, options: {})
BeverageFactory.build(drink, options).prepare
end
end
class BeverageFactory
def self.build(drink, options)
if drink == :coffee
Coffee.new(options: options)
elsif drink == :tea
Tea.new(options: options)
elsif drink == :cocoa
Cocoa.new(options: options)
end
end
end
class Coffee
def prepare
dispense_cup
heat_water
prepare_grounds
dispense_water
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
dispense_whipped_cream if options[:fluffy]
dispose_of_grounds
end
end
class Tea
def prepare
dispense_cup
heat_water
dispense_tea_bag
dispense_water
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
end
end
class Cocoa
def prepare
dispense_cup
heat_water
dispense_cocoa_mix
dispense_water
dispense_whipped_cream if options[:fluffy]
end
end
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☕ Refactor: Extract factory class
class CoffeeMachine
def vend(drink: :coffee, options: {})
BeverageFactory.build(drink, options).prepare
end
end
class BeverageFactory
def self.build(drink, options)
if drink == :coffee
Coffee.new(options: options)
elsif drink == :tea
Tea.new(options: options)
elsif drink == :cocoa
Cocoa.new(options: options)
else
NullBeverage.new(options: options)
end
end
end
class NullBeverage
def prepare
# no-op
end
end
class Coffee
def prepare
dispense_cup
heat_water
prepare_grounds
dispense_water
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
dispense_whipped_cream if options[:fluffy]
dispose_of_grounds
end
end
class Tea
def prepare
dispense_cup
heat_water
dispense_tea_bag
dispense_water
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
end
end
class Cocoa
def prepare
dispense_cup
heat_water
dispense_cocoa_mix
dispense_water
dispense_whipped_cream if options[:fluffy]
end
end
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☕ Refactor: Use convention to prevent churn
class CoffeeMachine
def vend(drink: :coffee, options: {})
BeverageFactory.build(drink, options).prepare
end
end
class BeverageFactory
def self.build(drink, options)
klass = drink.capitalize
if Module.const_defined?(klass)
Module.const_get(klass).new(options: options)
else
NullBeverage.new(options: options)
end
end
end
class NullBeverage
def prepare
# no-op
end
end
class Coffee
def prepare
dispense_cup
heat_water
prepare_grounds
dispense_water
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
dispense_whipped_cream if options[:fluffy]
dispose_of_grounds
end
end
class Tea
def prepare
dispense_cup
heat_water
dispense_tea_bag
dispense_water
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
end
end
class Cocoa
def prepare
dispense_cup
heat_water
dispense_cocoa_mix
dispense_water
dispense_whipped_cream if options[:fluffy]
end
end
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☕ Complexity of the CoffeeMachine class over time
Rehydrate
Extract Classes
Introduce Factory
Whipped Cream
Cocoa
Cream
Sweetener
DRY
Tea
Co
ff
ee
10
20
30
25
15
5
0
40
35
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☕ Complexity of the CoffeeMachine class over time
Rehydrate
Extract Classes
Introduce Factory
Whipped Cream
Cocoa
Cream
Sweetener
DRY
Tea
Co
ff
ee
10
20
30
25
15
5
0
40
35
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☕ Complexity of the CoffeeMachine class over time
Rehydrate
Extract Classes
Introduce Factory
Whipped Cream
Cocoa
Cream
Sweetener
DRY
Tea
Co
ff
ee
10
20
30
25
15
5
0
40
35
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☕ Complexity of the CoffeeMachine class over time
Rehydrate
Extract Classes
Introduce Factory
Whipped Cream
Cocoa
Cream
Sweetener
DRY
Tea
Co
ff
ee
10
20
30
25
15
5
0
40
35
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☕ Complexity of the application
Class Churn Complexity
--------------------- ----- ----------
CoffeeMachine#vend 10 3.9
BeverageFactory#build 2 6.2
Coffee#prepare 1 16.6
Tea#prepare 1 11.8
Cocoa#prepare 1 8.1
NullBeverage#prepare 1 0.0
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How to add functionality without modifying existing
fi
les.
Now, who wants ?
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☕ Refactor: Use convention to prevent churn
class CoffeeMachine
def vend(drink: :coffee, options: {})
BeverageFactory.build(drink, options).prepare
end
end
class BeverageFactory
def self.build(drink, options)
klass = drink.capitalize
if Module.const_defined?(klass)
Module.const_get(klass).new(options: options)
else
NullBeverage.new(options: options)
end
end
end
class NullBeverage
def prepare
# no-op
end
end
class Coffee
def prepare
dispense_cup
heat_water
prepare_grounds
dispense_water
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
dispense_whipped_cream if options[:fluffy]
dispose_of_grounds
end
end
class Tea
def prepare
dispense_cup
heat_water
dispense_tea_bag
dispense_water
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
end
end
class Cocoa
def prepare
dispense_cup
heat_water
dispense_cocoa_mix
dispense_water
dispense_whipped_cream if options[:fluffy]
end
end
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☕ Refactor: Use convention to prevent churn
class CoffeeMachine
def vend(drink: :coffee, options: {})
BeverageFactory.build(drink, options).prepare
end
end
class BeverageFactory
def self.build(drink, options)
klass = drink.capitalize
if Module.const_defined?(klass)
Module.const_get(klass).new(options: options)
else
NullBeverage.new(options: options)
end
end
end
class NullBeverage
def prepare
# no-op
end
end
class Soup
def prepare
dispense_cup
heat_water
dispense_condensed_soup
dispense_water
dispense_croutons if options[:crunchy]
dispense_hot_sauce if options[:spicy]
end
end
class Coffee
def prepare
dispense_cup
heat_water
prepare_grounds
dispense_water
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
dispense_whipped_cream if options[:fluffy]
dispose_of_grounds
end
end
class Tea
def prepare
dispense_cup
heat_water
dispense_tea_bag
dispense_water
dispense_sweetener if options[:sweet]
dispense_creamer if options[:creamy]
end
end
class Cocoa
def prepare
dispense_cup
heat_water
dispense_cocoa_mix
dispense_water
dispense_whipped_cream if options[:fluffy]
end
end
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Yeah, but does it scale?
How to apply this to a large, complicated code base.
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☕ Plotting complexity vs. churn
Churn
Complexity
Getting Empirical about Refactoring by Michael Feathers
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☕ Plotting complexity vs. churn
Pain Free
Churn
Complexity
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☕ Plotting complexity vs. churn
Pain Free
Painful
Churn
Complexity
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Pain Free
☕ Plotting complexity vs. churn
Painful
Configuration?
Churn
Complexity
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☕ Plotting complexity vs. churn
Pain Free
Painful
Configuration?
Omega Mess?
Churn
Complexity
Go Ahead, Make a Mess by Sandi Metz
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☕ Plotting complexity vs. churn
Churn
Complexity
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Conclusion
A Brewer’s Guide to Filtering out Complexity and Churn
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Take Aways
A Brewer’s Guide to Filtering out Complexity and Churn
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Take Aways
A Brewer’s Guide to Filtering out Complexity and Churn
Complexity will sneak into your code.
• Happens one commit at a time
• Conditionals and DRY are often the culprits
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Take Aways
A Brewer’s Guide to Filtering out Complexity and Churn
You can recognize complexity before it becomes painful.
• Keep methods short
• Watch complexity
• Pay attention to how it feels
Complexity will sneak into your code.
• Happens one commit at a time
• Conditionals and DRY are often the culprits
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Take Aways
A Brewer’s Guide to Filtering out Complexity and Churn
You can recognize complexity before it becomes painful.
• Keep methods short
• Watch complexity
• Pay attention to how it feels
And, you can back away from painful complexity.
• Polymorphism and factories are your friends
• Overly DRY code can hide abstractions and couple algorithms in dangerous ways
Complexity will sneak into your code.
• Happens one commit at a time
• Conditionals and DRY are often the culprits
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Homework
A Brewer’s Guide to Filtering out Complexity and Churn
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Homework
What is the average method complexity for your application?
• Use the Flog gem to measure complexity
A Brewer’s Guide to Filtering out Complexity and Churn
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Homework
What is the
fi
le with the most churn in your application?
• Use the Churn gem to measure churn
What is the average method complexity for your application?
• Use the Flog gem to measure complexity
A Brewer’s Guide to Filtering out Complexity and Churn
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Homework
What is the
fi
le with the most churn in your application?
• Use the Churn gem to measure churn
Which class in your application needs the most attention?
• Use the Ruby Critic gem to plot complexity vs. churn
• Look for the
fi
le with the highest complexity and churn
What is the average method complexity for your application?
• Use the Flog gem to measure complexity
A Brewer’s Guide to Filtering out Complexity and Churn
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EMAIL
fi
[email protected]
GITHUB
@Fito
TWITTER
@
fi
to.vonzastrow
EMAIL
[email protected]
GITHUB
@aridlehoover
TWITTER
@aridlehoover
BLOG
the.codegardener.com
GITHUB REPO
https://github.com/
fi
rst-try-software/co
ff
ee
Get in touch!
SLACK CHANNEL
#a-brewers-guide-to-
fi
ltering-out-complexity-and-churn
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Ruby Flog
Ruby Flog
VS Code extension that puts
fl
og scores in your status bar
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Thanks for coming!
A Brewer’s Guide to Filtering out Complexity and Churn
Sandi Metz
• Practical Object Oriented Design in Ruby (book)
• 99 Bottles of OOP (book) (sample on the topic of measuring complexity)
• Rules: https://youtu.be/npOGOmkxuio
• Go Ahead, Make a Mess: https://youtu.be/mpA2F1In41w
Ryan Davis
• Flog: https://github.com/seattlerb/
fl
og
Jake Scruggs
• https://jakescruggs.blogspot.com/2008/08/whats-good-
fl
og-score.html
Michael Feathers
• Working E
ff
ectively with Legacy Code (book)
• https://www.agileconnection.com/article/getting-empirical-about-refactoring
Alan Ridlehoover & Fito von Zastrow
• Ruby Flog: https://marketplace.visualstudio.com/items?itemName=
fi
rst-try-software.ruby-
fl
og