Applying the Module Builder Pattern

If you haven't heard of this pattern, you're not alone! The Module Builder pattern is a recently-coined Ruby metaprogramming technique that extends Module in order to provide configuration for the behavior encapsulated within. Think of it like a template for generating Modules that are customized to the place you use them.

It's a powerful pattern that is used within Rails and the Mobility gem, but can also directly apply to your application code. This talk will walk through a real life example showing you how.

Presented at Columbus Ruby Brigade

Transcript

1. Applying the Module Builder Pattern Bradley.Schaefer@stitchfix.com @soulcutter
2. Experiment Definitions
3. Control Cell Experiment Cell
4. Control Cell Experiment Cell LOSER LOSER
5. 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
6. 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
7. 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
8. 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
9. What stands out?
10. Duplication!
11. module ABExperiment def initialize(client) @client = client @api = Experiments::API.new(client, NAME) end end
12. module ABExperiment def initialize(client) @client = client @api = Experiments::API.new(client, NAME) end end
13. 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
14. 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
15. Let's run the tests!
16. 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
17. 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
18. 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
19. module ABExperiment def initialize(client) @client = client @api = Experiments::API.new( client, self.class.const_get(:NAME) ) end end
20. module ABExperiment def initialize(client) @client = client @api = Experiments::API.new( client, self.class::NAME ) end end
21. Tests Pass!
22. 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
23. 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
24. module ABExperiment attr_reader :api, :client def initialize(client) @client = client @api = Experiments::API.new( client, self.class.const_get(:NAME) ) end end
25. 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
26. 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
27. 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
28. 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
29. 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
30. 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
31. 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
32. Let's run the tests!
33. 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 #<Experiments::DSL>
34. 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 #<Experiments::DSL>
35. 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 #<Experiments::DSL>
36. 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
37. Tests Pass!
38. 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
39. 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
40. Why not a base class?
41. 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
42. 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
43. Still have work to do!
44. 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
45. 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
46. Module is a Class
47. ABExperiment = Module.new do # ... end module ABExperiment # ... end
48. ABExperiment = Module.new do # ... end include ABExperiment class ABExperimentBuilder < Module include ABExperimentBuilder.new(…)
49. ABExperiment = Module.new do # ... end include ABExperiment class ABExperimentBuilder < Module include ABExperimentBuilder.new(…)
50. 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
51. 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
52. 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
53. 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
54. class ABExperimentBuilder < Module # def initialize(…) module ClassMethods # ... same as before ... end def included(base) base.extend(ClassMethods) end end
55. 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
56. Let's talk tradeoffs
57. 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
58. Was this a good refactor?
59. When you might consider using this
60. 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
61. Shared behavior that needs configuration
62. Credits Chris Salzberg dejimata.com/2017/5/20/the-ruby-module-builder-pattern
63. Questions?
64. 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