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Applying the Module Builder Pattern [email protected] @soulcutter

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Experiment Definitions

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Control Cell Experiment Cell

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Control Cell Experiment Cell LOSER LOSER

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class BodyShape attr_reader :api, :client NAME = 'New Womens Body Shape Question' CONTROL_CELL = 'Control' TEST_CELL = 'New Question' def self.define! Experiments::Api.define_experiment do name NAME cell CONTROL_CELL, control: true cell TEST_CELL end end def initialize(client) @api = Experiments::Api.new(client, NAME) @client = client end def in_experiment? api.in_cell?(TEST_CELL) end end

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class ItemTypeGroupPreferences attr_reader :api, :client NAME = 'New Womens Item Type Group Preferences' CONTROL_CELL = 'Control' TEST_CELL = 'New Question' def self.define! Experiments::Api.define_experiment do name NAME cell CONTROL_CELL, control: true cell TEST_CELL end end def initialize(client) @api = Experiments::Api.new(client, NAME) @client = client end def in_experiment? api.in_cell?(TEST_CELL) end end

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class PrimaryObjectives attr_reader :api, :client NAME = 'New Womens Primary Reasons Question' CONTROL_CELL = 'Control' TEST_CELL = 'New Question' def self.define! Experiments::Api.define_experiment do name NAME cell CONTROL_CELL, control: true cell TEST_CELL end end def initialize(client) @api = Experiments::Api.new(client, NAME) @client = client end def in_experiment? api.in_cell?(TEST_CELL) && client.created_at > Date.new(2017) end end

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class WomensBrands attr_reader :api, :client NAME = 'New Womens Brand Question' CONTROL_CELL = 'Control' TEST_CELL = 'New Question' def self.define! Experiments::Api.define_experiment do name NAME cell CONTROL_CELL, control: true cell TEST_CELL end end def initialize(client) @api = Experiments::Api.new(client, NAME) @client = client end def in_experiment? api.in_cell?(TEST_CELL) end end

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What stands out?

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Duplication!

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module ABExperiment def initialize(client) @client = client @api = Experiments::API.new(client, NAME) end end

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module ABExperiment def initialize(client) @client = client @api = Experiments::API.new(client, NAME) end end

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class WomensBrands include ABExperiment attr_reader :api, :client NAME = 'New Womens Brand Question' CONTROL_CELL = 'Control' TEST_CELL = 'New Question' def self.define! Experiments::Api.define_experiment do name NAME cell CONTROL_CELL, control: true cell TEST_CELL end end def initialize(client) @api = Experiments::Api.new(client, NAME) @client = client end def in_experiment? api.in_cell?(TEST_CELL) end end

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class WomensBrands include ABExperiment attr_reader :api, :client NAME = 'New Womens Brand Question' CONTROL_CELL = 'Control' TEST_CELL = 'New Question' def self.define! Experiments::Api.define_experiment do name NAME cell CONTROL_CELL, control: true cell TEST_CELL end end def initialize(client) @api =Experiments::Api.new(client, NAME) @client = client end def in_experiment? api.in_cell?(TEST_CELL) end end

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Let's run the tests!

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module ABExperiment def initialize(client) @client = client @api = StitchFix::Experiments::API.new(client, NAME) end end Failure/Error: @api = Experiments::Api.new(client, NAME) NameError: uninitialized constant ABExperiment::NAME

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module ABExperiment def initialize(client) @client = client @api = Experiments::API.new(client, NAME) end end Failure/Error: @api = Experiments::Api.new(client, NAME) NameError: uninitialized constant ABExperiment::NAME

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module ABExperiment def initialize(client) @client = client @api = Experiments::API.new(client, NAME) end end Failure/Error: @api = Experiments::Api.new(client, NAME) NameError: uninitialized constant ABExperiment::NAME

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module ABExperiment def initialize(client) @client = client @api = Experiments::API.new( client, self.class.const_get(:NAME) ) end end

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module ABExperiment def initialize(client) @client = client @api = Experiments::API.new( client, self.class::NAME ) end end

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Tests Pass!

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class WomensBrands include ABExperiment attr_reader :api, :client NAME = 'New Womens Brand Question' CONTROL_CELL = 'Control' TEST_CELL = 'New Question' def self.define! Experiments::Api.define_experiment do name NAME cell CONTROL_CELL, control: true cell TEST_CELL end end def in_experiment? api.in_cell?(TEST_CELL) end end

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class WomensBrands include ABExperiment attr_reader :api, :client NAME = 'New Womens Brand Question' CONTROL_CELL = 'Control' TEST_CELL = 'New Question' def self.define! Experiments::Api.define_experiment do name NAME cell CONTROL_CELL, control: true cell TEST_CELL end end def in_experiment? api.in_cell?(TEST_CELL) end end

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module ABExperiment attr_reader :api, :client def initialize(client) @client = client @api = Experiments::API.new( client, self.class.const_get(:NAME) ) end end

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class WomensBrands include ABExperiment attr_reader :api, :client NAME = 'New Womens Brand Question' CONTROL_CELL = 'Control' TEST_CELL = 'New Question' def self.define! Experiments::Api.define_experiment do name NAME cell CONTROL_CELL, control: true cell TEST_CELL end end def in_experiment? api.in_cell?(TEST_CELL) end end

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class WomensBrands include ABExperiment NAME = 'New Womens Brand Question' CONTROL_CELL = 'Control' TEST_CELL = 'New Question' def self.define! Experiments::Api.define_experiment do name NAME cell CONTROL_CELL, control: true cell TEST_CELL end end def in_experiment? api.in_cell?(TEST_CELL) end end

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class WomensBrands include ABExperiment NAME = 'New Womens Brand Question' CONTROL_CELL = 'Control' TEST_CELL = 'New Question' def self.define! Experiments::Api.define_experiment do name NAME cell CONTROL_CELL, control: true cell TEST_CELL end end def in_experiment? api.in_cell?(TEST_CELL) end end

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module ABExperiment extend ActiveSupport::Concern # ... module ClassMethods def define! Experiments::API.define_experiment do name NAME cell CONTROL_CELL, control: true cell TEST_CELL end end end

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module ABExperiment extend ActiveSupport::Concern # ... module ClassMethods def define! Experiments::API.define_experiment do name NAME cell CONTROL_CELL, control: true cell TEST_CELL end end end

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module ABExperiment extend ActiveSupport::Concern # ... module ClassMethods def define! Experiments::API.define_experiment do name const_get(:NAME) cell const_get(:CONTROL_CELL), control: true cell const_get(:TEST_CELL) end end end

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class WomensBrands include ABExperiment NAME = 'New Womens Brand Question' CONTROL_CELL = 'Control' TEST_CELL = 'New Question' def self.define! Experiments::Api.define_experiment do name NAME cell CONTROL_CELL, control: true cell TEST_CELL end end def in_experiment? api.in_cell?(TEST_CELL) end end

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Let's run the tests!

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Experiments::API.define_experiment do name const_get(:NAME) cell const_get(:CONTROL_CELL), control: true cell const_get(:TEST_CELL) end Failure/Error: name const_get(:NAME) NoMethodError: undefined method `const_get' for #

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Experiments::API.define_experiment do name const_get(:NAME) cell const_get(:CONTROL_CELL), control: true cell const_get(:TEST_CELL) end Failure/Error: name const_get(:NAME) NoMethodError: undefined method `const_get' for #

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Experiments::API.define_experiment do name const_get(:NAME) cell const_get(:CONTROL_CELL), control: true cell const_get(:TEST_CELL) end Failure/Error: name const_get(:NAME) NoMethodError: undefined method `const_get' for #

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klass = self Experiments::API.define_experiment do name klass.const_get(:NAME) cell klass.const_get(:CONTROL_CELL), control: true cell klass.const_get(:TEST_CELL) end

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Tests Pass!

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class WomensBrands include ABExperiment NAME = 'New Womens Brand Question' CONTROL_CELL = 'Control' TEST_CELL = 'New Question' def in_experiment? api.in_cell?(TEST_CELL) end end

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module ABExperiment extend ActiveSupport::Concern attr_reader :client, :api def initialize(client) @client = client @api = Experiments::API.new( self.class.const_get(:NAME), client ) end module ClassMethods def define! klass = self Experiments::API.define_experiment do name klass.const_get(:NAME) cell klass.const_get(:CONTROL_CELL), control: true cell klass.const_get(:TEST_CELL) end end end end

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Why not a base class?

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class ABExperiment attr_reader :api, :client def initialize(client) @client = client @api = Experiments::API.new( self.class.const_get(:NAME), client ) end def self.define! klass = self Experiments::API.define_experiment do name klass.const_get(:NAME) cell klass.const_get(:CONTROL_CELL), control: true cell klass.const_get(:TEST_CELL) end end end

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class WomensBrands < ABExperiment include ABExperiment NAME = 'New Womens Brand Question' CONTROL_CELL = 'Control' TEST_CELL = 'New Question' def in_experiment? api.in_cell?(TEST_CELL) end end

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Still have work to do!

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class WomensBrands include ABExperiment NAME = 'New Womens Brand Question' CONTROL_CELL = 'Control' TEST_CELL = 'New Question' def in_experiment? api.in_cell?(TEST_CELL) end end

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class WomensBrands include ABExperimentBuilder.new( name: 'New Womens Brand Question' control: 'Control' test: 'New Question' ) def in_experiment? api.in_cell?(TEST_CELL) end end

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Module is a Class

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ABExperiment = Module.new do # ... end module ABExperiment # ... end

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ABExperiment = Module.new do # ... end include ABExperiment class ABExperimentBuilder < Module include ABExperimentBuilder.new(…)

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ABExperiment = Module.new do # ... end include ABExperiment class ABExperimentBuilder < Module include ABExperimentBuilder.new(…)

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class ABExperimentBuilder < Module def initialize(name:, control:, test:) attr_reader :api, :client const_set(:NAME, name) const_set(:CONTROL_CELL, control) const_set(:TEST_CELL, test) define_method(:initialize) do |client| @client = client @api = Experiments::API.new( self.class.const_get(:NAME), client ) end end end

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class ABExperimentBuilder < Module def initialize(name:, control:, test:) attr_reader :api, :client const_set(:NAME, name) const_set(:CONTROL_CELL, control) const_set(:TEST_CELL, test) define_method(:initialize) do |client| @client = client @api = Experiments::API.new( self.class.const_get(:NAME), client ) end end end

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class ABExperimentBuilder < Module def initialize(name:, control:, test:) attr_reader :api, :client const_set(:NAME, name) const_set(:CONTROL_CELL, control) const_set(:TEST_CELL, test) define_method(:initialize) do |client| @client = client @api = Experiments::API.new( self.class.const_get(:NAME), client ) end end end

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class ABExperimentBuilder < Module def initialize(name:, control:, test:) attr_reader :api, :client const_set(:NAME, name) const_set(:CONTROL_CELL, control) const_set(:TEST_CELL, test) define_method(:initialize) do |client| @client = client @api = Experiments::API.new( self.class.const_get(:NAME), client ) end end end

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class ABExperimentBuilder < Module # def initialize(…) module ClassMethods # ... same as before ... end def included(base) base.extend(ClassMethods) end end

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class WomensBrands include ABExperimentBuilder.new( name: 'New Womens Brand Question' control: 'Control' test: 'New Question' ) def in_experiment? api.in_cell?(TEST_CELL) end end

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Let's talk tradeoffs

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The Good The Bad Encapsulation Had to write a talk to explain the code Experiment class readability metaprogramming: bad Didn't change tests/interface Changing interface potentially valuable Create new experiments with less cut and paste code Builder class readability Ability to configure module is a powerful general idea

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Was this a good refactor?

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When you might consider using this

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class WomensBrands include ABExperiment ab_experiment( name: 'New Womens Brand Question' control: 'Control' test: 'New Question' ) def in_experiment? api.in_cell?(TEST_CELL) end end

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Shared behavior that needs configuration

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Credits Chris Salzberg dejimata.com/2017/5/20/the-ruby-module-builder-pattern

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Questions?

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class ABExperimentBuilder < Module def initialize(name:, control:, test:) attr_reader :api, :client const_set(:NAME, name) const_set(:CONTROL_CELL, control) const_set(:TEST_CELL, test) define_method(:initialize) do |client| @client = client @api = Experiments::API.new( self.class.const_get(:NAME), client ) end end module ClassMethods def define! klass = self Experiments::API.define_experiment do name klass.const_get(:NAME) cell klass.const_get(:CONTROL_CELL), control: true cell klass.const_get(:TEST_CELL) end end end def included(base); base.extend(ClassMethods) end end