Alan Ridlehoover & Fito von Zastrow RailsConf 2023 The Coffee Machine Talk A Brewer’s Guide to Filtering out Complexity and Churn

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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How did we get here? How complexity sneaks into a code base.

class CoffeeMachine def vend dispense_cup heat_water prepare_grounds dispense_water dispose_of_grounds end end ☕ Story: As a patron, I want coffee

☕ 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 heat_water dispense_tea_bag dispense_water end end end

☕ 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

☕ 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

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 ☕ Story: As a patron, I want cream

☕ 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

☕ 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

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 ☕ 7 commits: 9 conditionals 1 2 3 4 5 6 7 8 9

Do you smell that? How to recognize the problem before it becomes painful and frustrating. Rules by Sandi Metz Flog by Ryan Davis

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 ☕ Measuring complexity with the flog gem

☕ 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

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 ☕ Story: As a patron, I want tea

☕ 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

☕ 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

☕ 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

☕ 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_cream if options[:creamy] end dispose_of_grounds if drink == :coffee end end Churn 6 Complexity 21.3 10 20 30 25 15 5 0

☕ 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_cream 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

☕ 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_cream 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

☕ 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_cream 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 Complexity 25.5

Can we turn it around? How to fi lter out complexity and churn.

☕ 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_cream if options[:creamy] end unless drink == :tea dispense_whipped_cream if options[:fluffy] end dispose_of_grounds if drink == :coffee end end

☕ Refactor: Rehydrate to see missing abstractions

☕ 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_cream if options[:creamy] end unless drink == :tea dispense_whipped_cream if options[:fluffy] end dispose_of_grounds if drink == :coffee end end

☕ 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_cream 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_cream if options[:creamy] elsif drink == :cocoa dispense_cup heat_water dispense_cocoa_mix dispense_water dispense_whipped_cream if options[:fluffy] end end end

☕ 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 < Beverage def prepare dispense_cup heat_water prepare_grounds dispense_water dispense_sweetener if sweet? dispense_cream if creamy? dispense_whipped_cream if fluffy? dispose_of_grounds end end 
 class Tea < Beverage def prepare dispense_cup heat_water dispense_tea_bag dispense_water dispense_sweetener if sweet? dispense_cream if creamy? end end 
 class Cocoa < Beverage def prepare dispense_cup heat_water dispense_cocoa_mix dispense_water dispense_whipped_cream if fluffy? end end

☕ 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 < Beverage def prepare dispense_cup heat_water prepare_grounds dispense_water dispense_sweetener if sweet? dispense_cream if creamy? dispense_whipped_cream if fluffy? dispose_of_grounds end end 
 class Tea < Beverage def prepare dispense_cup heat_water dispense_tea_bag dispense_water dispense_sweetener if sweet? dispense_cream if creamy? end end 
 class Cocoa < Beverage def prepare dispense_cup heat_water dispense_cocoa_mix dispense_water dispense_whipped_cream if fluffy? end end

☕ Refactor: Extract polymorphic objects class CoffeeMachine def vend(drink: :coffee, options: {}) BeverageFactory.build(drink, options).prepare end end class BeverageFactory def self.build(beverage, options) if beverage == :coffee Coffee.new(options) elsif beverage == :tea Tea.new(options) elsif beverage == :cocoa Cocoa.new(options) end end end class Coffee < Beverage def prepare dispense_cup heat_water prepare_grounds dispense_water dispense_sweetener if sweet? dispense_cream if creamy? dispense_whipped_cream if fluffy? dispose_of_grounds end end 
 class Tea < Beverage def prepare dispense_cup heat_water dispense_tea_bag dispense_water dispense_sweetener if sweet? dispense_cream if creamy? end end 
 class Cocoa < Beverage def prepare dispense_cup heat_water dispense_cocoa_mix dispense_water dispense_whipped_cream if fluffy? end end

☕ Refactor: Introduce the NullObject pattern class CoffeeMachine def vend(drink: :coffee, options: {}) BeverageFactory.build(drink, options).prepare end end class BeverageFactory def self.build(beverage, options) if beverage == :coffee Coffee.new(options) elsif beverage == :tea Tea.new(options) elsif beverage == :cocoa Cocoa.new(options) else NullBeverage.new(options) end end end class NullBeverage < Beverage def prepare # no-op end end class Coffee < Beverage def prepare dispense_cup heat_water prepare_grounds dispense_water dispense_sweetener if sweet? dispense_cream if creamy? dispense_whipped_cream if fluffy? dispose_of_grounds end end 
 class Tea < Beverage def prepare dispense_cup heat_water dispense_tea_bag dispense_water dispense_sweetener if sweet? dispense_cream if creamy? end end 
 class Cocoa < Beverage def prepare dispense_cup heat_water dispense_cocoa_mix dispense_water dispense_whipped_cream if fluffy? end end

☕ 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(beverage, options) klass = beverage.capitalize if Module.const_defined?(klass) Module.const_get(klass).new(options) else NullBeverage.new(options) end end end class NullBeverage < Beverage def prepare # no-op end end class Coffee < Beverage def prepare dispense_cup heat_water prepare_grounds dispense_water dispense_sweetener if sweet? dispense_cream if creamy? dispense_whipped_cream if fluffy? dispose_of_grounds end end 
 class Tea < Beverage def prepare dispense_cup heat_water dispense_tea_bag dispense_water dispense_sweetener if sweet? dispense_cream if creamy? end end 
 class Cocoa < Beverage def prepare dispense_cup heat_water dispense_cocoa_mix dispense_water dispense_whipped_cream if fluffy? end end

Self Registration How to create an open/closed factory class. 🚧

☕ Refactor: Introduce self-registration class CoffeeMachine def vend(drink: :coffee, options: {}) BeverageFactory.build(drink, options).prepare end end class BeverageFactory def self.build(beverage, options) klass = beverage.capitalize if Module.const_defined?(klass) Module.const_get(klass).new(options) else NullBeverage.new(options) end end end class NullBeverage < Beverage def prepare # no-op end end class Coffee < Beverage def prepare dispense_cup heat_water prepare_grounds dispense_water dispense_sweetener if sweet? dispense_cream if creamy? dispense_whipped_cream if fluffy? dispose_of_grounds end end 
 class Tea < Beverage def prepare dispense_cup heat_water dispense_tea_bag dispense_water dispense_sweetener if sweet? dispense_cream if creamy? end end class Cocoa < Beverage def prepare dispense_cup heat_water dispense_cocoa_mix dispense_water dispense_whipped_cream if fluffy? end end

☕ Refactor: Introduce self-registration class CoffeeMachine def vend(drink: :coffee, options: {}) BeverageFactory.build(drink, options).prepare end end class BeverageFactory def self.build(key, options) beverage_class(key).new(options) end def self.register(key, klass) beverages[key] = klass end def self.beverage_class(key) beverages[key] || NullBeverage end def self.beverages @beverages ||= {} end end class NullBeverage < Beverage def prepare # no-op end end class Coffee < Beverage BeverageFactory.register(:coffee, self) def prepare dispense_cup heat_water prepare_grounds dispense_water dispense_sweetener if sweet? dispense_cream if creamy? dispense_whipped_cream if fluffy? dispose_of_grounds end end 
 class Tea < Beverage BeverageFactory.register(:tea, self) def prepare dispense_cup heat_water dispense_tea_bag dispense_water dispense_sweetener if sweet? dispense_cream if creamy? end end class Cocoa < Beverage BeverageFactory.register(:cocoa, self) def prepare dispense_cup heat_water dispense_cocoa_mix dispense_water dispense_whipped_cream if fluffy? end end

☕ Refactor: Introduce self-registration class Coffee < Beverage BeverageFactory.register(:coffee, self) def prepare dispense_cup heat_water prepare_grounds dispense_water dispense_sweetener if sweet? dispense_cream if creamy? dispense_whipped_cream if fluffy? dispose_of_grounds end end 
 class Tea < Beverage BeverageFactory.register(:tea, self) def prepare dispense_cup heat_water dispense_tea_bag dispense_water dispense_sweetener if sweet? dispense_cream if creamy? end end class Cocoa < Beverage BeverageFactory.register(:cocoa, self) def prepare dispense_cup heat_water dispense_cocoa_mix dispense_water dispense_whipped_cream if fluffy? end end class CoffeeMachine def vend(drink: :coffee, options: {}) BeverageFactory.build(drink, options).prepare end end class BeverageFactory def self.build(key, options) beverage_class(key).new(options) end def self.register(key, klass) beverages[key] = klass end def self.beverage_class(key) beverages[key] || NullBeverage end def self.beverages @beverages ||= {} end end class NullBeverage < Beverage def prepare # no-op end end

☕ Refactor: Introduce self-registration class Coffee < Beverage BeverageFactory.register(:coffee, self) def prepare dispense_cup heat_water prepare_grounds dispense_water dispense_sweetener if sweet? dispense_cream if creamy? dispense_whipped_cream if fluffy? dispose_of_grounds end end 
 class Tea < Beverage BeverageFactory.register(:tea, self) def prepare dispense_cup heat_water dispense_tea_bag dispense_water dispense_sweetener if sweet? dispense_cream if creamy? end end class Cocoa < Beverage BeverageFactory.register(:cocoa, self) def prepare dispense_cup heat_water dispense_cocoa_mix dispense_water dispense_whipped_cream if fluffy? end end class CoffeeMachine def vend(drink: :coffee, options: {}) BeverageFactory.build(drink, options).prepare end end class BeverageFactory def self.build(key, options) beverage_class(key).new(options) end def self.register(key, klass) beverages[key] = klass end def self.beverage_class(key) beverages[key] || NullBeverage end def self.beverages @beverages ||= {} end end class NullBeverage < Beverage def prepare # no-op end end

☕ Refactor: Introduce self-registration class Coffee < Beverage BeverageFactory.register(:coffee, self) def prepare dispense_cup heat_water prepare_grounds dispense_water dispense_sweetener if sweet? dispense_cream if creamy? dispense_whipped_cream if fluffy? dispose_of_grounds end end 
 class Tea < Beverage BeverageFactory.register(:tea, self) def prepare dispense_cup heat_water dispense_tea_bag dispense_water dispense_sweetener if sweet? dispense_cream if creamy? end end class Cocoa < Beverage BeverageFactory.register(:cocoa, self) def prepare dispense_cup heat_water dispense_cocoa_mix dispense_water dispense_whipped_cream if fluffy? end end class CoffeeMachine def vend(drink: :coffee, options: {}) BeverageFactory.build(drink, options).prepare end end class BeverageFactory def self.build(key, options) beverage_class(key).new(options) end def self.register(key, klass) beverages[key] = klass end def self.beverage_class(key) beverages[key] || NullBeverage end def self.beverages @beverages ||= {} end end class NullBeverage < Beverage def prepare # no-op end end

class CoffeeMachine def vend(drink: :coffee, options: {}) BeverageFactory.build(drink, options).prepare end end class BeverageFactory def self.build(key, options) beverage_class(key).new(options) end def self.register(key, klass) beverages[key] = klass end def self.beverage_class(key) beverages[key] || NullBeverage end def self.beverages @beverages ||= {} end end class NullBeverage < Beverage def prepare # no-op end end class Coffee < Beverage BeverageFactory.register(:coffee, self) 
 def prepare dispense_cup heat_water prepare_grounds dispense_water dispense_sweetener if sweet? dispense_cream if creamy? dispense_whipped_cream if fluffy? dispose_of_grounds end end 
 class Tea < Beverage BeverageFactory.register(:tea, self) def prepare dispense_cup heat_water dispense_tea_bag dispense_water dispense_sweetener if sweet? dispense_cream if creamy? end end class Cocoa < Beverage BeverageFactory.register(:cocoa, self) def prepare dispense_cup heat_water dispense_cocoa_mix dispense_water dispense_whipped_cream if fluffy? end end ☕ Refactor: Introduce self-registration

class CoffeeMachine def vend(drink: :coffee, options: {}) BeverageFactory.build(drink, options).prepare end end class BeverageFactory def self.build(key, options) beverage_class(key).new(options) end def self.register(key, klass) beverages[key] = klass end def self.beverage_class(key) beverages[key] || NullBeverage end def self.beverages @beverages ||= {} end end class NullBeverage < Beverage def prepare # no-op end end # { # :coffee => Coffee, 
 # :tea => Tea, # :cocoa => Cocoa # ) class Coffee < Beverage BeverageFactory.register(:coffee, self) def prepare dispense_cup heat_water prepare_grounds dispense_water dispense_sweetener if sweet? dispense_cream if creamy? dispense_whipped_cream if fluffy? dispose_of_grounds end end 
 class Tea < Beverage BeverageFactory.register(:tea, self) def prepare dispense_cup heat_water dispense_tea_bag dispense_water dispense_sweetener if sweet? dispense_cream if creamy? end end class Cocoa < Beverage BeverageFactory.register(:cocoa, self) def prepare dispense_cup heat_water dispense_cocoa_mix dispense_water dispense_whipped_cream if fluffy? end end ☕ Refactor: Introduce self-registration

class CoffeeMachine def vend(drink: :coffee, options: {}) BeverageFactory.build(drink, options).prepare end end class BeverageFactory def self.build(key, options) beverage_class(key).new(options) end def self.register(key, klass) beverages[key] = klass end def self.beverage_class(key) beverages[key] || NullBeverage end def self.beverages @beverages ||= {} end end class NullBeverage < Beverage def prepare # no-op end end class Coffee < Beverage BeverageFactory.register(:coffee, self) def prepare dispense_cup heat_water prepare_grounds dispense_water dispense_sweetener if sweet? dispense_cream if creamy? dispense_whipped_cream if fluffy? dispose_of_grounds end end 
 class Tea < Beverage BeverageFactory.register(:tea, self) def prepare dispense_cup heat_water dispense_tea_bag dispense_water dispense_sweetener if sweet? dispense_cream if creamy? end end class Cocoa < Beverage BeverageFactory.register(:cocoa, self) def prepare dispense_cup heat_water dispense_cocoa_mix dispense_water dispense_whipped_cream if fluffy? end end ☕ Refactor: Introduce self-registration

class CoffeeMachine def vend(drink: :coffee, options: {}) BeverageFactory.build(drink, options).prepare end end class BeverageFactory def self.build(key, options) beverage_class(key).new(options) end def self.register(key, klass) beverages[key] = klass end def self.beverage_class(key) beverages[key] || NullBeverage end def self.beverages @beverages ||= {} end end class NullBeverage < Beverage def prepare # no-op end end class Coffee < Beverage BeverageFactory.register(:coffee, self) def prepare dispense_cup heat_water prepare_grounds dispense_water dispense_sweetener if sweet? dispense_cream if creamy? dispense_whipped_cream if fluffy? dispose_of_grounds end end 
 class Tea < Beverage BeverageFactory.register(:tea, self) def prepare dispense_cup heat_water dispense_tea_bag dispense_water dispense_sweetener if sweet? dispense_cream if creamy? end end class Cocoa < Beverage BeverageFactory.register(:cocoa, self) def prepare dispense_cup heat_water dispense_cocoa_mix dispense_water dispense_whipped_cream if fluffy? end end ☕ Refactor: Introduce self-registration

class CoffeeMachine def vend(drink: :coffee, options: {}) BeverageFactory.build(drink, options).prepare end end class BeverageFactory def self.build(key, options) beverage_class(key).new(options) end def self.register(key, klass) beverages[key] = klass end def self.beverage_class(key) beverages[key] || NullBeverage end def self.beverages @beverages ||= {} end end class NullBeverage < Beverage def prepare # no-op end end class Coffee < Beverage prepares :coffee def prepare dispense_cup heat_water prepare_grounds dispense_water dispense_sweetener if sweet? dispense_cream if creamy? dispense_whipped_cream if fluffy? dispose_of_grounds end end 
 class Tea < Beverage prepares :tea def prepare dispense_cup heat_water dispense_tea_bag dispense_water dispense_sweetener if sweet? dispense_cream if creamy? end end class Beverage def self.prepares(key) BeverageFactory.register(key, self) end # initializer & other shared code end class Cocoa < Beverage prepares :cocoa def prepare dispense_cup heat_water dispense_cocoa_mix dispense_water dispense_whipped_cream if fluffy? end end ☕ Refactor: Introduce self-registration

☕ Refactor: Introduce self-registration class CoffeeMachine def vend(drink: :coffee, options: {}) BeverageFactory.build(drink, options).prepare end end class BeverageFactory def self.build(key, options) beverage_class(key).new(options) end def self.register(key, klass) beverages[key] = klass end def self.beverage_class(key) beverages[key] || NullBeverage end def self.beverages @beverages ||= {} end end class NullBeverage < Beverage def prepare # no-op end end class Coffee < Beverage prepares :coffee def prepare dispense_cup heat_water prepare_grounds dispense_water dispense_sweetener if sweet? dispense_cream if creamy? dispense_whipped_cream if fluffy? dispose_of_grounds end end 
 class Tea < Beverage prepares :tea def prepare dispense_cup heat_water dispense_tea_bag dispense_water dispense_sweetener if sweet? dispense_cream if creamy? end end class Beverage def self.prepares(key) BeverageFactory.register(key, self) end # initializer & other shared code end class Cocoa < Beverage prepares :cocoa def prepare dispense_cup heat_water dispense_cocoa_mix dispense_water dispense_whipped_cream if fluffy? end end

https://github.com/ fi rst-try-software/manufacturable ☕ Manufacturable: A gem for self-registration

Did that work? Were we able to reduce the complexity?

☕ 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

☕ 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

☕ 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

☕ Complexity of the CoffeeMachine class over time Rehydrate Extract Classes Introduce Factory
 and self-registration Whipped Cream Cocoa Cream Sweetener DRY Tea Co ff ee 10 20 30 25 15 5 0 40 35

☕ Complexity of the application Class Churn Complexity --------------------- ----- ---------- CoffeeMachine 10 3.9 BeverageFactory 3 1.8 Beverage 2 2.2 
 Coffee 1 16.6 Tea 1 11.8 Cocoa 1 8.1 NullBeverage 1 0.0

Now, who wants ? How to add functionality without modifying existing fi les.

☕ Refactor: Introduce self-registration class CoffeeMachine def vend(drink: :coffee, options: {}) BeverageFactory.build(drink, options).prepare end end class BeverageFactory def self.build(key, options) beverage_class(key).new(options) end def self.register(key, klass) beverages[key] = klass end def self.beverage_class(key) beverages[key] || NullBeverage end def self.beverages @beverages ||= {} end end class NullBeverage < Beverage def prepare # no-op end end class Coffee < Beverage prepares :coffee def prepare dispense_cup heat_water prepare_grounds dispense_water dispense_sweetener if sweet? dispense_cream if creamy? dispense_whipped_cream if fluffy? dispose_of_grounds end end 
 class Tea < Beverage prepares :tea def prepare dispense_cup heat_water dispense_tea_bag dispense_water dispense_sweetener if sweet? dispense_cream if creamy? end end class Beverage def self.prepares(key) BeverageFactory.register(key, self) end # initializer & other shared code end class Cocoa < Beverage prepares :cocoa def prepare dispense_cup heat_water dispense_cocoa_mix dispense_water dispense_whipped_cream if fluffy? end end

☕ Refactor: Introduce self-registration class CoffeeMachine def vend(drink: :coffee, options: {}) BeverageFactory.build(drink, options).prepare end end class BeverageFactory def self.build(key, options) beverage_class(key).new(options) end def self.register(key, klass) beverages[key] = klass end def self.beverage_class(key) beverages[key] || NullBeverage end def self.beverages @beverages ||= {} end end class NullBeverage < Beverage def prepare # no-op end end class Coffee < Beverage prepares :coffee def prepare dispense_cup heat_water prepare_grounds dispense_water dispense_sweetener if sweet? dispense_cream if creamy? dispense_whipped_cream if fluffy? dispose_of_grounds end end 
 class Tea < Beverage prepares :tea def prepare dispense_cup heat_water dispense_tea_bag dispense_water dispense_sweetener if sweet? dispense_cream if creamy? end end class Beverage def self.prepares(key) BeverageFactory.register(key, self) end # initializer & other shared code end class Cocoa < Beverage prepares :cocoa def prepare dispense_cup heat_water dispense_cocoa_mix dispense_water dispense_whipped_cream if fluffy? end end class TomatoSoup < Beverage prepares :tomato_soup def prepare dispense_cup heat_water dispense_condensed_soup dispense_water dispense_croutons if crunchy? dispense_hot_sauce if spicy? end end

☕ Refactor: Introduce self-registration class CoffeeMachine def vend(drink: :coffee, options: {}) BeverageFactory.build(drink, options).prepare end end class BeverageFactory def self.build(key, options) beverage_class(key).new(options) end def self.register(key, klass) beverages[key] = klass end def self.beverage_class(key) beverages[key] || NullBeverage end def self.beverages @beverages ||= {} end end class NullBeverage < Beverage def prepare # no-op end end class Coffee < Beverage prepares :coffee def prepare dispense_cup heat_water prepare_grounds dispense_water dispense_sweetener if sweet? dispense_cream if creamy? dispense_whipped_cream if fluffy? dispose_of_grounds end end 
 class Tea < Beverage prepares :tea def prepare dispense_cup heat_water dispense_tea_bag dispense_water dispense_sweetener if sweet? dispense_cream if creamy? end end class Beverage def self.prepares(key) BeverageFactory.register(key, self) end # initializer & other shared code end class Cocoa < Beverage prepares :cocoa def prepare dispense_cup heat_water dispense_cocoa_mix dispense_water dispense_whipped_cream if fluffy? end end

☕ Refactor: Introduce self-registration class CoffeeMachine def vend(drink: :coffee, options: {}) BeverageFactory.build(drink, options).prepare end end class BeverageFactory def self.build(key, options) beverage_class(key).new(options) end def self.register(key, klass) beverages[key] = klass end def self.beverage_class(key) beverages[key] || NullBeverage end def self.beverages @beverages ||= {} end end class NullBeverage < Beverage def prepare # no-op end end class Coffee < Beverage prepares :coffee def prepare dispense_cup heat_water prepare_grounds dispense_water dispense_sweetener if sweet? dispense_cream if creamy? dispense_whipped_cream if fluffy? dispose_of_grounds end end 
 class Tea < Beverage prepares :tea def prepare dispense_cup heat_water dispense_tea_bag dispense_water dispense_sweetener if sweet? dispense_cream if creamy? end end class Beverage def self.prepares(key) BeverageFactory.register(key, self) end # initializer & other shared code end class Cocoa < Beverage prepares :cocoa def prepare dispense_cup heat_water dispense_cocoa_mix dispense_water dispense_whipped_cream if fluffy? end end class TomatoSoup < Beverage prepares :tomato_soup def prepare dispense_cup heat_water dispense_condensed_soup dispense_water dispense_croutons if crunchy? dispense_hot_sauce if spicy? end end

☕ Refactor: Introduce self-registration class CoffeeMachine def vend(drink: :coffee, options: {}) BeverageFactory.build(drink, options).prepare end end class BeverageFactory def self.build(key, options) beverage_class(key).new(options) end def self.register(key, klass) beverages[key] = klass end def self.beverage_class(key) beverages[key] || NullBeverage end def self.beverages @beverages ||= {} end end class NullBeverage < Beverage def prepare # no-op end end class Coffee < Beverage prepares :coffee def prepare dispense_cup heat_water prepare_grounds dispense_water dispense_sweetener if sweet? dispense_cream if creamy? dispense_whipped_cream if fluffy? dispose_of_grounds end end 
 class Tea < Beverage prepares :tea def prepare dispense_cup heat_water dispense_tea_bag dispense_water dispense_sweetener if sweet? dispense_cream if creamy? end end class Beverage def self.prepares(key) BeverageFactory.register(key, self) end # initializer & other shared code end class Cocoa < Beverage prepares :cocoa def prepare dispense_cup heat_water dispense_cocoa_mix dispense_water dispense_whipped_cream if fluffy? end end class TomatoSoup < Beverage prepares :tomato_soup def prepare dispense_cup heat_water dispense_condensed_soup dispense_water dispense_croutons if crunchy? dispense_hot_sauce if spicy? end end class AppleCider < Beverage prepares :apple_cider def prepare dispense_cup heat_water dispense_cider_mix dispense_water dispense_cinnamon_stick end end

Yeah, but does it scale? How to apply this to a large, complicated code base.

☕ Plotting complexity vs. churn Churn Complexity Getting Empirical about Refactoring by Michael Feathers

☕ Plotting complexity vs. churn Churn Complexity Pain Free

☕ Plotting complexity vs. churn Pain Free Painful Churn Complexity

☕ Plotting complexity vs. churn Pain Free Painful Churn Complexity Configuration?

☕ Plotting complexity vs. churn Pain Free Painful Churn Complexity Configuration? Omega Mess? Go Ahead, Make a Mess by Sandi Metz

☕ Plotting complexity vs. churn Churn Complexity

☕ Plotting complexity vs. churn Churn Complexity

☕ Plotting complexity vs. churn Churn Complexity

Conclusion A Brewer’s Guide to Filtering out Complexity and Churn

Take Aways A Brewer’s Guide to Filtering out Complexity and Churn

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

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 You can recognize complexity before it becomes painful. • Keep methods short • Watch complexity • Pay attention to how it feels

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 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 • Self-registration can take you across the no-churn fi nish line

Homework A Brewer’s Guide to Filtering out Complexity and Churn

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

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

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

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 Where might you use self-registration in your code? • Play with the technique fi rst to get a feel for it • Look at the Manufacturable gem for industrial-scale self-registration

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 A 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 • Manufacturable: https://github.com/ fi rst-try-software/manufacturable • Ruby Flog: https://marketplace.visualstudio.com/items?itemName= fi rst-try-software.ruby- fl og