In Relentless Pursuit of Rest

"That's not very RESTful." As a Rails developer you've probably heard or even spoken that proclamation before, but what does it really mean? What's so great about being RESTful anyway?

RESTful architecture can narrow the responsibilities of your Rails controllers and make follow-on refactorings more natural. In this talk, you'll learn to refactor code to follow RESTful principles and to identify the positive impact those changes have throughout your application stack.

Transcript

1. In Relentless Pursuit of REST
2. Derek Prior @derekprior
3. What is REST?
4. That's not very RESTful
5. HTTP
6. Hypermedia
7. HATEOAS
8. It Doesn't Matter
9. What Does Matter?
10. Nouns
11. Verbs
12. Resources & Actions
13. More Small Things
15. Custom Actions
17. resource :user, only: [:edit, :update] do get :edit_password, on: :member put :update_password, on: :member end
18. Longhand Definitions get '/user/edit_password', to: 'users#edit_password' put '/user/update_password', to: 'users#update_password'
19. Controller Mappings
20. Controller Mappings • users#edit_password
21. Controller Mappings • users#edit_password • users#update_password
22. Controller Mappings • users#edit_password • users#update_password • noun#verb_noun
23. Controller Mappings
24. Controller Mappings • passwords#edit
25. Controller Mappings • passwords#edit • passwords#update
26. Controller Mappings • passwords#edit • passwords#update • noun#verb
27. Controller Mappings Before After users#edit_password passwords#edit users#update_password passwords#update
28. resource :user, only: [:edit, :update] do resource :password, only: [:edit, :update] end
29. class PasswordsController < ApplicationController def edit # what used to be `users#edit_password` end def update # what used to be `users#update_password` end end
31. That's not worth another controller!
32. Password isn't a model!
33. Controllers do not need to map to ActiveRecord objects
34. Complex Actions
35. No one sets out to write complex controllers
36. def update @photo = current_user.photos.find(params[:id]) if @photo.update(update_photo_params) redirect_to @photo else render :edit end end private def update_photo_params params.require(:photo).permit(:caption) end
37. As a user, I want to mark a photo as featured so it is displayed prominently on my profile.
38. As a user, I want to mark a photo as featured so it is displayed prominently on my profile. • Oh, and I should only be allowed to have one featured photo
39. As a user, I want to mark a photo as featured so it is displayed prominently on my profile. • Oh, and I should only be allowed to have one featured photo • Oh, and if I un-feature a photo, my first photo should automatically be featured
40. def update @photo = current_user.photos.find(params[:id]) @photo.assign_attributes(update_photo_params) if @photo.valid? && update_photo(photo) redirect_to @photo else render :edit end end private def update_photo(photo) ApplicationRecord.transaction do if photo.featured_changed? && photo.featured? current_user.photos.featured.update!(featured: false) elsif photo.featured_changed? && !photo.featured? current_user.photos.first.update!(featured: true) end photo.save! end end
41. def update_photo(photo) ApplicationRecord.transaction do if photo.featured_changed? && photo.featured? current_user.photos.featured.update!(featured: false) elsif photo.featured_changed? && !photo.featured? current_user.photos.first.update!(featured: true) end photo.save! end end
42. def update @photo = current_user.photos.find(params[:id]) @photo.assign_attributes(update_photo_params) if @photo.valid? && update_photo(photo) redirect_to @photo else render :edit end end private def update_photo(photo) ApplicationRecord.transaction do if photo.featured_changed? && photo.featured? current_user.photos.featured.update!(featured: false) elsif photo.featured_changed? && !photo.featured? current_user.photos.first.update!(featured: true) end photo.save! end end
43. Differing Perspectives
44. resources :photos, only: [:new, :edit, :create, :update] do resource :featured_flag, only: [:create, :destroy] end
45. class FeaturedFlagsController < ApplicationController def create @photo = current_user.photos.find(params[:photo_id]) if AddFeaturedFlag.to(@photo) redirect_to photos_path else redirect_to photos_path, error: t('.error') end end def destroy @photo = current_user.photos.find(params[:photo_id]) if RemoveFeaturedFlag.from(@photo) redirect_to photos_path else redirect_to photos_path, error: t('.error') end end end
46. def create @photo = current_user.photos.find(params[:photo_id]) if AddFeaturedFlag.to(@photo) redirect_to photos_path else redirect_to photos_path, error: t('.error') end end
47. def destroy @photo = current_user.photos.find(params[:photo_id]) if RemoveFeaturedFlag.from(@photo) redirect_to photos_path else redirect_to photos_path, error: t('.error') end end
48. class AddFeaturedFlag def self.to(photo) new(photo).call end def initialize(photo) @photo = photo end def call ApplicationRecord.transaction do @photo.user.photos.featured.update!(featured: false) @photo.update!(featured: true) end end end
49. Be Boring
50. Ambiguous Language
51. resources :orders do put :process, on: :member end
54. Language Matters
55. Noun: Order Verb: process
56. class OrdersController < ApplicationController before_action :find_order, except: [:index] before_action #... before_action #... before_action :ensure_processable, only: [:process] before_action #... # a bunch of actions def process # procedure for processing an order # potentially very complicated order.update!(process_params) end # more actions private # dozens of private methods useful to various actions end
57. Noun: Order Verb: ship
58. resources :orders do put :ship, on: :member end
59. resources :orders do resource :shipment, only: [:create] end
60. class ShipmentsController < ApplicationController before_action :ensure_processable def create # procedure for processing an order # potentially very complicated order.update!(shipment_params) end private # a subset of those dozens of private methods end
62. I see duplication!
63. You didn't improve the code!
64. Breathing Room
67. State Machines
68. State Machines on Rails
69. resources :orders do member do put :authorize put :capture put :refund put :reject end end
70. state_machine initial: :pending do before_transition captured: :refunded, do: :ensure_refundable after_transition captured: :refunded, do: :process_refund after_transition authorized: :captured, do: :capture_payment after_transition pending: :rejected, do: :void_order after_transition pending: :authorized, do: :authorize_payment #... end
71. state_machine initial: :pending do # callbacks... event :authorize do transition pending: :authorized end event :capture do transition authorized: :captured end event :refund do transition captured: :refunded end event :reject do transition all => :rejected end end
72. state_machine initial: :pending do # callbacks... # events... state :captured do validates :reward_points, presence: true end state :rejected do validate :validates_tax_exemption end end
73. state_machine initial: :pending do before_transition captured: :refunded, do: :ensure_refundable after_transition captured: :refunded, do: :process_refund after_transition authorized: :captured, do: :capture_payment after_transition pending: :rejected, do: :void_order after_transition pending: :authorized, do: :authorize_payment event :authorize do transition pending: :authorized end event :capture do transition authorized: :captured end event :refund do transition captured: :refunded end event :reject do transition all => :rejected end state :captured do validates :reward_points, presence: true end state :pending do validate :validates_tax_emption end end
75. What if update didn't exist?
76. resources :orders, only: [:new, :create] do resource :authorization, only: [:create] resource :capture, only: [:create] resource :refund, only: [:create] resource :rejection, only: [:create] end
77. class Authorization def initialize(order) @order = order end def process raise unless authorizable? ApplicationRecord.transaction do @order.update!(state: "authorized") PaymentGateway.authorize(@order.payment_method, @order.total) end end private def authorizable? # Is the order in a state where it can be authorized? end end
78. Outside In
80. This is fine for CRUD apps, but...
81. Imagination
82. Be CRUDdy
83. Be Boring
84. Be RESTful
85. Questions?
86. Derek Prior • twitter: @derekprior • email: derek@thoughtbot.com • podcast: http://bikeshed.fm