Exploiting The Resource Idiom

Scottish Ruby Conference 2012

Transcript

1. For smaller, simpler, and more readily understandable Rails web apps Exploiting The RESource Idiom! Tuesday, July 3, 12
2. @mattyoho Tuesday, July 3, 12
3. @mattyoho @EdgeCase Tuesday, July 3, 12
4. @mattyoho @NewContext Tuesday, July 3, 12
5. @mattyoho @NewContext @HungryAcademy Tuesday, July 3, 12
6. Conventio figura Thinking is hard Tuesday, July 3, 12
7. Conventio figura Rails requires less Thinking is hard Tuesday, July 3, 12
8. http://www.etsy.com/shop/weelittlestitches Patterns! Tuesday, July 3, 12
9. http://www.etsy.com/shop/weelittlestitches Patterns! REST! Tuesday, July 3, 12
10. Representational State Transfer on Rails! Tuesday, July 3, 12
11. Resources “Nouns” of the system (At least from an external perspective... ...return to that later) Tuesday, July 3, 12
12. HTTP Provides the shared set of verbs, and their semantics, for interacting with the system’s nouns, i.e. resources Tuesday, July 3, 12
13. Features Such as... •Routes •respond_to/with •Default view rendering •Rails Tuesday, July 3, 12
14. Memory Footprint Tuesday, July 3, 12
15. Memory Footprint Simpler... Tuesday, July 3, 12
16. Memory Footprint Simpler... Smaller... Tuesday, July 3, 12
17. Memory Footprint Simpler... Easier to understand Smaller... Tuesday, July 3, 12
18. Caveat! Tuesday, July 3, 12
19. Reader beware! These ideas should be considered my opinion! They are options, context dependent, Caveat Emptor! Tuesday, July 3, 12
20. How about an example?! Tuesday, July 3, 12
21. Feeds! Tuesday, July 3, 12
22. User Item Feed 1 1 1 0..* Diagram! Tuesday, July 3, 12
23. Feedlr::Application.routes.draw do root to: 'feeds#index' resources :feeds, only: [:index, :show] resources :items, except: :index end Routes! Tuesday, July 3, 12
24. New Feature Refeed Tuesday, July 3, 12
25. Refeed Let’s add some methods! Tuesday, July 3, 12
26. Feedlr::Application.routes.draw do root to: 'feeds#index' resources :feeds, only: [:index, :show] resources :items, except: :index do member do post :refeed end end end Routes! Tuesday, July 3, 12
27. Routes! Feedlr::Application.routes.draw do root to: 'feeds#index' resources :feeds, only: [:index, :show] resources :items, except: :index do member do post :refeed end end end Tuesday, July 3, 12
28. class ItemsController < ApplicationController before_filter :require_login respond_to :html, :json def new @item = Item.new respond_with(@item) end def create; end def destroy; end # etc. end CRUD Tuesday, July 3, 12
29. class ItemsController < ApplicationController before_filter :require_login respond_to :html, :json def new @item = Item.new respond_with(@item) end def create; end def destroy; end def refeed # impl. end end CRUD? Tuesday, July 3, 12
30. CRUD? class ItemsController < ApplicationController before_filter :require_login respond_to :html, :json def new @item = Item.new respond_with(@item) end def create; end def destroy; end def refeed # impl. end end Tuesday, July 3, 12
31. class ItemsController < ApplicationController before_filter :require_login def refeed feed = current_user.feed item = feed.items.find(params[:id]) attrs = item.attributes.merge(refed_item: item) feed.items.create(attrs) redirect_to(feed) end end MEMBER Tuesday, July 3, 12
32. Feedlr::Application.routes.draw do root to: 'feeds#index' resources :feeds, only: [:index, :show] resources :items, except: :index do member do post :refeed delete :remove_refeed end end end Routes! Tuesday, July 3, 12
33. Routes! Feedlr::Application.routes.draw do root to: 'feeds#index' resources :feeds, only: [:index, :show] resources :items, except: :index do member do post :refeed delete :remove_refeed end end end Tuesday, July 3, 12
34. class ItemsController < ApplicationController before_filter :require_login def refeed feed = current_user.feed item = feed.items.find(params[:id]) attrs = item.attributes.merge(refed_item: item) feed.items.create(attrs) redirect_to(feed) end end MEMBER Tuesday, July 3, 12
35. ARGH! class ItemsController < ApplicationController before_filter :require_login def refeed feed = current_user.feed item = feed.items.find(params[:id]) attrs = item.attributes.merge(refed_item: item) feed.items.create(attrs) redirect_to(feed) end def remove_refeed end end Tuesday, July 3, 12
36. Trouble When programming, we should prefer to generalize from the specific Tuesday, July 3, 12
37. Edge Cases! Are bad! Tuesday, July 3, 12
38. Edge Cases! (That’s why we changed our name.) Are bad! Tuesday, July 3, 12
39. Feedlr::Application.routes.draw do root to: 'feeds#index' resources :feeds, only: [:index, :show] resources :items, except: :index do member do post :refeed delete :remove_refeed end end end Routes! Tuesday, July 3, 12
40. Feedlr::Application.routes.draw do root to: 'feeds#index' resources :feeds, only: [:index, :show] resources :items, except: :index do resources :refeeds, only: [:create, :destroy] end end Nested! Tuesday, July 3, 12
41. ARGH! class ItemsController < ApplicationController before_filter :require_login def refeed feed = current_user.feed item = feed.items.find(params[:id]) attrs = item.attributes.merge(refed_item: item) feed.items.create(attrs) redirect_to(feed) end def remove_refeed end end Tuesday, July 3, 12
42. class RefeedsController < ApplicationController before_filter :require_login def create feed = current_user.feed item = feed.items.find(params[:item_id]) attrs = item.attributes.merge(refed_item: item) feed.items.create(attrs) redirect_to(feed) end def destroy end end ARGH? Tuesday, July 3, 12
43. ARGH? class RefeedsController < ApplicationController before_filter :require_login def create feed = current_user.feed item = feed.items.find(params[:item_id]) attrs = item.attributes.merge(refed_item: item) feed.items.create(attrs) redirect_to(feed) end def destroy end end Tuesday, July 3, 12
44. class Refeed def initialize(feed,item) @feed = feed @item = item end def create atrs = @item.attributes.merge(refed_item: item) @feed.items.create(atrs) end def destroy; end end app/lib Tuesday, July 3, 12
45. class RefeedsController < ApplicationController before_filter :require_login def create feed = current_user.feed item = feed.items.find(params[:item_id]) attrs = item.attributes.merge(refed_item: item) feed.items.create(attrs) redirect_to(feed) end def destroy end end ARGH? Tuesday, July 3, 12
46. class RefeedsController < ApplicationController before_filter :require_login def create feed = current_user.feed item = feed.items.find(params[:item_id]) refeed = Refeed.new(feed, item) refeed.create redirect_to(feed) end def destroy end end MEH! Tuesday, July 3, 12
47. If you’re introducing non-”RESTful” methods into a controller, you’re probably missing a top- level concept that should be a first-class resource. Tuesday, July 3, 12
48. Resources DO NOT have to be backed by database tables! Shocking, I know. Tuesday, July 3, 12
49. Across town, trouble brews! Tuesday, July 3, 12
50. Danger looms in Rails City... Tuesday, July 3, 12
51. Danger looms in Rails City... Our apps strain under the weight of our code! Tuesday, July 3, 12
52. def new @feed_item = FeedItem.new respond_to do |format| format.html format.json { render json: @feed_item } end end def edit @feed_item = current_user.feed.feed_items.find(params[:id]) end def create kind = params[:feed_item].delete(:kind) @feed_item = current_user.feed.feed_item_of(kind).new(params[:feed_item]) respond_to do |format| if @feed_item.save format.html { redirect_to current_user.feed, notice: 'Feed item was successfully created.' } format.json { render json: @feed_item, status: :created, location: @feed_item } else format.html { render action: "new" } format.json { render json: @feed_item.errors, status: :unprocessable_entity } end end end def update @feed_item = current_user.feed.feed_items.find(params[:id]) respond_to do |format| if @feed_item.update_attributes(params[:feed_item]) format.html { redirect_to current_user.feed, notice: 'Feed item was successfully updated.' } format.json { head :no_content } else format.html { render action: "edit" } format.json { render json: @feed_item.errors, status: :unprocessable_entity } end end end def destroy @feed_item = current_user.feed.feed_items.find(params[:id]) @feed_item.destroy respond_to do |format| format.html { redirect_to root_url } format.json { head :no_content } end end def destroy @feed_item = current_user.feed.feed_items.find(params[:id]) @feed_item.destroy respond_to do |format| format.html { redirect_to root_url } format.json { head :no_content } end end def destroy @feed_item = current_user.feed.feed_items.find(params[:id]) @feed_item.destroy respond_to do |format| format.html { redirect_to root_url } format.json { head :no_content } end end Tuesday, July 3, 12
53. Fat models Skinny Controllers Tuesday, July 3, 12
54. But the beast broke free! Tuesday, July 3, 12
55. def new @feed_item = FeedItem.new respond_to do |format| format.html format.json { render json: @feed_item } end end def edit @feed_item = current_user.feed.feed_items.find(params[:id]) end def create kind = params[:feed_item].delete(:kind) @feed_item = current_user.feed.feed_item_of(kind).new(params[:feed_item]) respond_to do |format| if @feed_item.save format.html { redirect_to current_user.feed, notice: 'Feed item was successfully created.' } format.json { render json: @feed_item, status: :created, location: @feed_item } else format.html { render action: "new" } format.json { render json: @feed_item.errors, status: :unprocessable_entity } end end end def update @feed_item = current_user.feed.feed_items.find(params[:id]) respond_to do |format| if @feed_item.update_attributes(params[:feed_item]) format.html { redirect_to current_user.feed, notice: 'Feed item was successfully updated.' } format.json { head :no_content } else format.html { render action: "edit" } format.json { render json: @feed_item.errors, status: :unprocessable_entity } end end end def destroy @feed_item = current_user.feed.feed_items.find(params[:id]) @feed_item.destroy respond_to do |format| format.html { redirect_to root_url } format.json { head :no_content } end end def destroy @feed_item = current_user.feed.feed_items.find(params[:id]) @feed_item.destroy respond_to do |format| format.html { redirect_to root_url } format.json { head :no_content } end end def destroy @feed_item = current_user.feed.feed_items.find(params[:id]) @feed_item.destroy respond_to do |format| format.html { redirect_to root_url } format.json { head :no_content } end end Tuesday, July 3, 12
56. HAHAHA! Methods! Tuesday, July 3, 12
57. Go back to the well... Tuesday, July 3, 12
58. Navigate Model View Controller Model View Controller Tuesday, July 3, 12
59. MVC Trygve Reenskaug DCI Tuesday, July 3, 12
60. The largely static data model of the application, captures user and programmer knowledge about what the system is. Data Tuesday, July 3, 12
61. A mapping from one or more data objects to roles in the system. Implements one or more system use cases. CONTEXT Tuesday, July 3, 12
62. Captures behavior, or what the system does. Corresponds to the user’s mental model of action. Stateless, and relies on a data object in a context. Interaction Tuesday, July 3, 12
63. (Roles) Captures behavior, or what the system does. Corresponds to the user’s mental model of action. Stateless, and relies on a data object in a context. Tuesday, July 3, 12
64. Navigate Model View Controller Role View Controller Data Context Tuesday, July 3, 12
65. class User < AR::Base # Data end module ComicBookReading # Role def read ... end end # Context? user = User.new user.extend ComicBookReading user.read() Tuesday, July 3, 12
66. class ComicBookReaderController def update # Context? user = current_user user.extend ComicBookReading user.read() end end Tuesday, July 3, 12
67. Coupling! Mixins == Inheritance Tuesday, July 3, 12
68. Navigate Model View Controller Model View Controller Tuesday, July 3, 12
69. Request Model View Controller Controller View Model Tuesday, July 3, 12
70. The Dark Model Saga! Tuesday, July 3, 12
71. class RefeedsController < ApplicationController before_filter :require_login def create feed = current_user.feed item = feed.items.find(params[:item_id]) refeed = Refeed.new(feed, item) refeed.create redirect_to(feed) end def destroy end end MEH! Tuesday, July 3, 12
72. module ResourceModel def self.inherited(inheritor) inheritor.class_eval do include ActiveModel::Naming include ActiveModel::Validations include ActiveModel::Translation end end attr_reader :attributes, :errors def initialize(attributes = {}) @attributes = attributes @errors = ActiveModel::Errors.new(self) end end app/Mixins Tuesday, July 3, 12
73. module ResourceModel def to_key; nil end def to_param; nil end def to_partial_path; ”" end def valid? errors.empty? end def persisted?; false end def read_attribute_for_validation(key) @attributes[key] end end app/Mixins Tuesday, July 3, 12
74. class Refeed def initialize(feed,item) @feed = feed @item = item end def create atrs = @item.attributes.merge(refed_item: item) @feed.items.create(atrs) end def destroy; end end app/lib Tuesday, July 3, 12
75. class Refeed include ResourceModel def self.find_by_feed_and_item_id(feed, item_id) ... end def save feed = attributes[:feed] item = feed.items.find(attributes[:item_id]) atrs = item.attributes.merge(refed_item: item) feed.items.create(atrs) end end app/models Tuesday, July 3, 12
76. app/models class Refeed include ResourceModel def self.find_by_feed_and_item_id(feed, item_id) ... end def save feed = attributes[:feed] item = feed.items.find(attributes[:item_id]) atrs = item.attributes.merge(refed_item: item) feed.items.create(atrs) end end Tuesday, July 3, 12
77. class RefeedsController < ApplicationController before_filter :require_login def create feed = current_user.feed item = feed.items.find(params[:item_id]) refeed = Refeed.new(feed, item) refeed.create redirect_to(feed) end def destroy end end Meh! Tuesday, July 3, 12
78. class RefeedsController < ApplicationController before_filter :require_login def create feed = current_user.feed item = feed.find(params[:item_id]) refeed = Refeed.new(feed: feed, item: item) if refeed.save redirect_to refeed_path(refeed) end end def destroy end end Okay! Tuesday, July 3, 12
79. class RefeedsController < ApplicationController def create ... end def destroy feed = current_user.feed item_id = params[:item_id] refeed = Refeed.find_by_feed_and_item_id( feed: feed, item_id: item_id) refeed.destroy redirect_to feed end end Okay! Tuesday, July 3, 12
80. But does it make sense? Tuesday, July 3, 12
81. Interface Don’t have the same surface area as AR::Base objects Tuesday, July 3, 12
82. Anemic names Refeed#save doesn’t seem descriptive Tuesday, July 3, 12
83. Unless! We cast Refeed as a resource abstraction with CRUD semantics! domain Tuesday, July 3, 12
84. Bookkeeping In this case, we draw a line between HTTP book- keeping and problem domain Tuesday, July 3, 12
85. It’s a spectrum! Tuesday, July 3, 12
86. Food for thought, anyway Tuesday, July 3, 12
87. Food for thought, anyway That said... Tuesday, July 3, 12
88. Don’t get in Rails’ way. Tuesday, July 3, 12
89. http://www.etsy.com/shop/weelittlestitches Tuesday, July 3, 12
90. Mental Model! Tuesday, July 3, 12
91. THANKS! See you next time! Questions? @mattyoho @NewContext Tuesday, July 3, 12