Refinements in Ruby

In Ruby 2.0, refinements were introduced as a language-level feature. Since then they haven't seen wide-spread adoption in the community; it's time to change that! We'll walk through what refinements are, how they work, and what problems they can solve. Come see better ways to organize your spaghetti code without sacrificing readability.

Transcript

1. Refinements in Ruby twitter.com/kddeisz
2. twitter.com/kddeisz Refinements in Ruby class C def foo puts "C#foo" end end
3. twitter.com/kddeisz Refinements in Ruby class C def foo puts "C#foo" end end module M refine C do def foo puts "C#foo in M" end end end
4. twitter.com/kddeisz Refinements in Ruby class C def foo puts "C#foo" end end module M refine C do def foo puts "C#foo in M" end end end
5. twitter.com/kddeisz Refinements in Ruby class C def foo puts "C#foo" end end module M refine C do def foo puts "C#foo in M" end end end
6. twitter.com/kddeisz Refinements in Ruby class C def foo puts "C#foo" end end module M refine C do def foo puts "C#foo in M" end end end using M c = C.new
7. twitter.com/kddeisz Refinements in Ruby class C def foo puts "C#foo" end end module M refine C do def foo puts "C#foo in M" end end end using M c = C.new
8. twitter.com/kddeisz Refinements in Ruby class C def foo puts "C#foo" end end module M refine C do def foo puts "C#foo in M" end end end using M c = C.new
9. twitter.com/kddeisz Refinements in Ruby class C def foo puts "C#foo" end end module M refine C do def foo puts "C#foo in M" end end end using M c = C.new c.foo # prints "C#foo in M"
10. Usage
12. Law of Demeter
13. Law of Demeter Common interfaces
14. Law of Demeter Common interfaces Local monkey-patches
15. twitter.com/kddeisz Refinements in Ruby class Organization < ApplicationRecord has_many :events has_many :users end class Event < ApplicationRecord belongs_to :host, class_name: 'User' belongs_to :organization has_many :rsvps end class Rsvp < ApplicationRecord belongs_to :event belongs_to :user end class User < ApplicationRecord belongs_to :organization has_many :hosted_events, foreign_key: :host_id, class_name: 'Event' has_many :rsvps end
16. Law of Demeter
17. Law of Demeter Only talk to your friends
18. twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord belongs_to :event validate :allowed_by_event? private def allowed_by_event? !event.invite_only? || rsvp.status_was == 'invited' end end class Event < ApplicationRecord has_many :rsvps end
19. twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord belongs_to :event validate :allowed_by_event? private def allowed_by_event? (!event.invite_only? || rsvp.status_was == 'invited') && (event.cap? && event.rsvps.size <= event.cap - 1) end end class Event < ApplicationRecord has_many :rsvps end
20. twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord belongs_to :event validate :allowed_by_event? private def allowed_by_event? (!event.invite_only? || rsvp.status_was == 'invited') && (event.cap? && event.rsvps.size <= event.cap - 1) end end class Event < ApplicationRecord has_many :rsvps end
21. twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord belongs_to :event validate :allowed_by_event? private def allowed_by_event? (!event.invite_only? || rsvp.status_was == 'invited') && (event.cap? && event.rsvps.size <= event.cap - 1) end end class Event < ApplicationRecord has_many :rsvps end
22. twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord belongs_to :event validate :allowed_by_event? private def allowed_by_event? (!event.invite_only? || rsvp.status_was == 'invited') && (event.cap? && event.rsvps.size <= event.cap - 1) end end class Event < ApplicationRecord has_many :rsvps end
23. twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord belongs_to :event validate :allowed_by_event? private def allowed_by_event? event.allowed_rsvp?(status_was) end end class Event < ApplicationRecord has_many :rsvps def allowed_rsvp?(status_was) (!invite_only? || status_was == 'invited') && (cap? && rsvps.size <= cap - 1) end end
24. twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord belongs_to :event validate { event.allowed_rsvp?(status_was) } end class Event < ApplicationRecord has_many :rsvps def allowed_rsvp?(status_was) (!invite_only? || status_was == 'invited') && (cap? && rsvps.size <= cap - 1) end end
25. twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord using Module.new { refine Event do def allowed_rsvp?(status_was) (!invite_only? || status_was == 'invited') && (cap? && rsvps.size <= cap - 1) end end } belongs_to :event validate { event.allowed_rsvp?(status_was) } end class Event < ApplicationRecord has_many :rsvps end
26. twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord belongs_to :event validate { event.allowed_rsvp?(status_was) } end class Event < ApplicationRecord has_many :rsvps def allowed_rsvp?(status_was) (!invite_only? || status_was == 'invited') && (cap? && rsvps.size <= cap - 1) end end
27. twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord belongs_to :event validate { event.allowed_rsvp?(status_was) } end class Event < ApplicationRecord has_many :rsvps def allowed_rsvp?(status_was) (!invite_only? || status_was == 'invited') && (cap? && rsvps.size <= cap - 1) end end
28. twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord using Module.new { refine Event do def allowed_rsvp?(status_was) (!invite_only? || status_was == 'invited') && (cap? && rsvps.size <= cap - 1) end end } belongs_to :event validate { event.allowed_rsvp?(status_was) } end class Event < ApplicationRecord has_many :rsvps end
29. twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << [ event.name, event.type, event.starts_at, event.ends_at, event.sponsored, event.rvsps.size ] end end end end
30. twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << [ event.name, event.type, event.starts_at, event.ends_at, event.sponsored, event.rvsps.size ] end end end end
31. twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << [ event.name, event.type, event.starts_at, event.ends_at, event.sponsored, event.rvsps.size ] end end end end
32. twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << [ event.name, event.type, event.starts_at, event.ends_at, event.sponsored, event.rvsps.size ] end end end end
33. twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << [ event.name, event.type, event.starts_at, event.ends_at, event.sponsored, event.rvsps.size ] end end end end
34. twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << [ event.name, event.type, event.starts_at, event.ends_at, event.sponsored, event.rvsps.size ] end end end end
35. twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << [ event.name, event.type, event.starts_at, event.ends_at, event.sponsored, event.rvsps.size ] end end end end
36. twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << to_row(event) end end end private def to_row(event) [ event.name, event.type, event.starts_at, event.ends_at, event.sponsored, event.rvsps.size ] end end
37. twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << event.to_row end end end end class Event < ApplicationRecord def to_row [ name, type, starts_at, ends_at, sponsored, rvsps.size ] end end
38. twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob using Module.new { refine Event do def to_row [ name, type, starts_at, ends_at, sponsored, rvsps.size ] end end } def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << event.to_row end end end end
39. twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << event.to_row end end end end class Event < ApplicationRecord def to_row [ name, type, starts_at, ends_at, sponsored, rvsps.size ] end end
40. twitter.com/kddeisz Refinements in Ruby class EventExportJob < ApplicationJob using Module.new { refine Event do def to_row [ name, type, starts_at, ends_at, sponsored, rvsps.size ] end end } def perform(organization) Export.generate(organization) do |export| organization.events.each do |event| export << event.to_row end end end end
41. Common interfaces
42. twitter.com/kddeisz Refinements in Ruby class User < ApplicationRecord def can_admin_organization? superuser? end end
43. twitter.com/kddeisz Refinements in Ruby class User < ApplicationRecord def can_admin_event?(event) event.host == self end def can_admin_organization? superuser? end end
44. twitter.com/kddeisz Refinements in Ruby class User < ApplicationRecord def can_admin_event?(event) event.host == self end def can_admin_organization? superuser? end def can_admin_rsvp?(rsvp) rsvp.user == self || can_admin_event?(rsvp.event) end end
45. twitter.com/kddeisz Refinements in Ruby class User < ApplicationRecord def can_admin?(record) case record when Event record.host == self when Organization superuser? when Rsvp record.user == self || can_admin?(record.event) else raise ArgumentError end end end
46. twitter.com/kddeisz Refinements in Ruby class User < ApplicationRecord def can_admin?(record) record.admin?(self) end end class Event < ApplicationRecord def admin?(user) host == user end end class Organization < ApplicationRecord def admin?(user) user.superuser? end end class Rsvp < ApplicationRecord def admin?(other) user == other || event.admin?(other) end end
47. twitter.com/kddeisz Refinements in Ruby class User < ApplicationRecord using Module.new { refine Event do def admin?(user) host == user end end refine Organization do def admin?(user) user.superuser? end end refine Rsvp do def admin?(other) user == other || event.admin?(other) end end } def can_admin?(record) record.admin?(self) ennd
48. twitter.com/kddeisz Refinements in Ruby class AdminRules < Struct.new(:user) using Module.new { refine Event do def admin?(user) host == user end end refine Organization do def admin?(user) user.superuser? end end refine Rsvp do def admin?(other) user == other || event.admin?(other) end end } def can_admin?(record) record.admin?(user) ennd
49. twitter.com/kddeisz Refinements in Ruby class AdminRules < Struct.new(:user) using Module.new { refine Event do def admin?(user) host == user end end refine Organization do def admin?(user) user.superuser? end end refine Rsvp do def admin?(other) user == other || event.admin?(other) end end } def can_admin?(record) record.admin?(user) ennd class User < ApplicationRecord delegate :can_admin?, to: :admin_rules def admin_rules AdminRules.new(self) end end
50. twitter.com/kddeisz Refinements in Ruby class AdminRules < Struct.new(:user) using Module.new { refine Event do def admin?(user) host == user end end refine Organization do def admin?(user) user.superuser? end end refine Rsvp do def admin?(other) user == other || event.admin?(other) end end } def can_admin?(record) record.admin?(user) ennd class User < ApplicationRecord delegate :can_admin?, to: :admin_rules def admin_rules AdminRules.new(self) end end
51. Local monkey-patches
52. twitter.com/kddeisz Refinements in Ruby class Hash def except(*keys) slice(*self.keys - keys) end end class UsersController < ApplicationController def update if @user.update(params[:user].except(:admin)) render @user, status: :success else render @user.errors, status: :unprocessable_entity end end end
53. twitter.com/kddeisz Refinements in Ruby class UsersController < ApplicationController using Module.new { refine Hash do def except(*keys) slice(*self.keys - keys) end end } def update if @user.update(params[:user].except(:admin)) render @user, status: :success else render @user.errors, status: :unprocessable_entity end end end
54. twitter.com/kddeisz Refinements in Ruby class Object def blank? respond_to?(:empty?) ? !!empty? : !self end end class NilClass def blank? true end end class FalseClass def blank? true end end class TrueClass def blank? false end end class Array alias_method :blank?, :empty? end class Hash alias_method :blank?, :empty? end class String def blank? empty? || BLANK_RE.match?(self) end end
55. twitter.com/kddeisz Refinements in Ruby module Blank refine Object do def blank? respond_to?(:empty?) ? !!empty? : !self end end refine NilClass do def blank? true end end refine FalseClass do def blank? true end end refine TrueClass do def blank? false end ennd module Blank refine Array do alias_method :blank?, :empty? end refine Hash do alias_method :blank?, :empty? end refine String do def blank? empty? || BLANK_RE.match?(self) end end end
56. twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord before_validation do self.message = message.blank? ? nil : message end end
57. twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord using Blank before_validation do self.message = message.blank? ? nil : message end end
58. twitter.com/kddeisz Refinements in Ruby class Rsvp < ApplicationRecord using ActiveSupport::StringExtensions before_validation do self.message = message.blank? ? nil : message end end
59. Conclusions
60. Code that changes together should live together
61. Refinements can move code out of class definitions and into where it is used
62. Use refinements to organize your code so developers don’t have to open so many files to make changes
63. Refinements in Ruby twitter.com/kddeisz