What the hell is ActiveSupport::Concern?

A short talk about ActiveSupport::Concern.

Transcript

1. Thanks!
2. Hark
3. Substantial
4. What the hell is ActiveSupport::Concern?
5. I have no idea.
6. U Concerned, Bro?
7. Aaron Patterson @tenderlove
8. Lead Pun Architect
9. Substantial, Thanks
11. Gorbachev Puff-Puff Thunderhorse
18. Rails Core ~ 3 years (I think)
19. Confession
20. What’s in a name?
21. Classes ❤ File ❤ Hash ❤ Set ❤ Array
22. Modules ❤ Enumerable ❤ Comparable
23. AS::Concern
24. “Concern” is a noun
25. “Concern” is a noun
26. “Son, We’re Concerned”
27. Grown Man.
28. Stay Classy Change Your Self Track Dependents
29. Stay Classy.
30. Class Methods module MyEnumerable def my_first end module ClassMethods def my_new end end def self.included(klass) klass.extend ClassMethods end end
31. Including class Aaron include MyEnumerable end p Aaron.respond_to?(:my_new) # => true p Aaron.new.respond_to?(:my_first) # => true
32. With Concern module MyEnumerable extend ActiveSupport::Concern def my_first end module ClassMethods def my_new end end end
33. Including class Aaron include MyEnumerable end p Aaron.respond_to?(:my_new) # => true p Aaron.new.respond_to?(:my_first) # => true
34. Be Careful!
35. Normal Include module MyEnumerable def my_first end end class Aaron p singleton_methods # => [] include MyEnumerable p singleton_methods # => [] end
36. Normal Extend module MyEnumerable def my_first end end class Aaron p singleton_methods # => [] extend MyEnumerable p singleton_methods # => [:my_first] end
37. Users May Be Surprised
38. Do I need this?
39. Are you coupled?
40. Change Your Self.
41. Setting up ivars
42. Class Accessor module MyEnumerable module ClassMethods attr_accessor :foo end def self.included klass klass.extend ClassMethods end end
43. Warning! class Aaron include MyEnumerable p foo end
44. Warning! class Aaron include MyEnumerable p foo end @foo not initialized
45. Class Accessor module MyEnumerable module ClassMethods attr_accessor :foo end def self.included klass klass.extend ClassMethods @foo = 10 end end
46. Class Accessor module MyEnumerable module ClassMethods attr_accessor :foo end def self.included klass klass.extend ClassMethods @foo = 10 end end self == MyEnumerable
47. Class Accessor module MyEnumerable module ClassMethods attr_accessor :foo end def self.included klass klass.extend ClassMethods klass.class_eval do @foo = 10 end end end
48. Working Code class Aaron include MyEnumerable p foo # => 10 end
49. With Concern module MyEnumerable extend ActiveSupport::Concern module ClassMethods attr_accessor :foo end included do @foo = 10 end end self == included class
50. Isolating Setup
51. Class Method Calls class Foo < ActiveRecord::Base scope :foo, -> { ... } scope :bar, -> { ... } scope :baz, -> { ... } # other methods end
52. Module Extraction module Findable def self.included(klass) klass.scope :foo, -> { ... } klass.scope :bar, -> { ... } klass.scope :baz, -> { ... } end end
53. Module Extraction module Findable def self.included(klass) klass.scope :foo, -> { ... } klass.scope :bar, -> { ... } klass.scope :baz, -> { ... } end end
54. class_eval module Findable def self.included(klass) klass.class_eval do scope :foo, -> { ... } scope :bar, -> { ... } scope :baz, -> { ... } end end end
55. Concerned module Findable extend ActiveSupport::Concern included do scope :foo, -> { ... } scope :bar, -> { ... } scope :baz, -> { ... } end end
56. Track Your Dependents.
57. Two Modules module Foo module ClassMethods def some_method end # .... end end module Bar def self.included klass klass.some_method end end
58. Bar depends on Foo
59. Usage class Aaron include Foo include Bar end
60. Usage - BOOM! class Aaron include Bar include Foo end
61. Try to Fix module Foo module ClassMethods def some_method end end end module Bar include Foo def self.included klass klass.some_method end end
62. Try to Fix module Foo module ClassMethods def some_method end end end module Bar include Foo def self.included klass klass.some_method end end
63. Fix with class_eval module Bar def self.included klass klass.class_eval do include Foo end klass.some_method end end
64. Concerned module Bar extend ActiveSupport::Concern include Foo included do some_method end end
65. Concerned module Bar extend ActiveSupport::Concern include Foo included do some_method end end NOT Ruby’s Include
66. When should I be concerned?
67. You probably shouldn’t be.
68. Can you simplify?
69. Many Dependencies
70. THANKS!