Rails Engines - Lessons Learned

This talk was performed at SpreeConf 2012 and a slightly shorter/modified version at Ruby on Ales in Bend Oregon, March 2012.

It covers the lessons that I've learned from building engines and working with them on massive scale applications. Two engines mentioned prominently in this talk are the Forem (https://github.com/radar/forem) and Spree (https://github.com/spree/spree), with some mentions of others, such as Devise.

Great information for those looking to get started with engines!

Transcript

1. Saturday, 3 March 12
2. How my curiosity about new features in Ruby on Rails... Saturday, 3 March 12
3. ... kind of sort of... Saturday, 3 March 12
4. ...indirectly led me to getting a new job... Saturday, 3 March 12
5. ...where I do awesome “stuff”... Saturday, 3 March 12
6. ...for an awesome community... Saturday, 3 March 12
7. ...and exactly what that awesome “stuff” entails. Saturday, 3 March 12
8. aka “Namespacing: Good for the soul” Saturday, 3 March 12
9. Ryan Bigg Saturday, 3 March 12
10. Ryan Bigg @ryanbigg Saturday, 3 March 12
11. Ryan Bigg Radar @ryanbigg Saturday, 3 March 12
12. Saturday, 3 March 12
13. Saturday, 3 March 12
14. Saturday, 3 March 12
15. Saturday, 3 March 12
16. Saturday, 3 March 12
17. Saturday, 3 March 12
18. Saturday, 3 March 12
19. Saturday, 3 March 12
20. 26,890 reputation top 0.67% of all time Saturday, 3 March 12
21. Saturday, 3 March 12
22. 1% Saturday, 3 March 12
23. Saturday, 3 March 12
24. Community Manager Community Manager Saturday, 3 March 12
25. Saturday, 3 March 12
26. Saturday, 3 March 12
27. Saturday, 3 March 12
28. Saturday, 3 March 12
29. Saturday, 3 March 12
30. Saturday, 3 March 12
31. Saturday, 3 March 12
32. 1,784 commits Saturday, 3 March 12
33. 1,784 commits (or roughly, 30%) Saturday, 3 March 12
34. Engines Engines Saturday, 3 March 12
35. James Adam James Adam Saturday, 3 March 12
36. Oct 31, 2005 Oct 31, 2005 Saturday, 3 March 12
37. 0.14.2 0.14.2 Rails Rails Saturday, 3 March 12
38. Kevin Smith Kevin Smith Saturday, 3 March 12
39. “[engines are a] nasty hack that breaks every new version of Rails” http://glu.ttono.us/articles/2006/08/30/guide-things-you-shouldnt-be-doing-in-rails Saturday, 3 March 12
40. “Stop trying to write ‘neato ajax driven thingies’” http://glu.ttono.us/articles/2006/08/30/guide-things-you-shouldnt-be-doing-in-rails Saturday, 3 March 12
41. Saturday, 3 March 12
42. “I didn't want Rails to succumb to the lure of high-level components like login systems, forums, content management, and the likes.” - DHH http://david.heinemeierhansson.com/arc/000407.html Saturday, 3 March 12
43. Saturday, 3 March 12
44. Saturday, 3 March 12
45. Saturday, 3 March 12
46. Saturday, 3 March 12
47. “But the goal of Rails is to create a world where [engines] are neither needed or strongly desired. Obviously, we are not quite there yet.” - DHH http://weblog.rubyonrails.org/2005/11/11/why-engines-and- components-are-not-evil-but-distracting Saturday, 3 March 12
48. “Engines have not received the blessing of the RoR core team, and I wouldn't expect any different, because it would be madness to include them in the core Rails.” - James Adam http://article.gmane.org/gmane.comp.lang.ruby.rails/29166 Saturday, 3 March 12
49. Madness! Saturday, 3 March 12
50. Engine Support Rails < 2.3 Use engines plugin https://github.com/lazyatom/engines Saturday, 3 March 12
51. Engine Support Rails 2.3 LOL http://railscasts.com/episodes/149-rails-engines Saturday, 3 March 12
52. Yehuda Katz Yehuda Katz Saturday, 3 March 12
53. Piotr Sarnacki Piotr Sarnacki Saturday, 3 March 12
54. Saturday, 3 March 12
55. Engine Support Rails 3.0 - Not bad Saturday, 3 March 12
56. Engine Support Rails 3.1 - OH YEAH Saturday, 3 March 12
57. Saturday, 3 March 12
58. Saturday, 3 March 12
59. Before Spree 1.0 Saturday, 3 March 12
60. Saturday, 3 March 12
61. Spree Product App path/to/engine/app/models/product.rb Product Saturday, 3 March 12
62. Spree Product App Product path/to/app/app/models/product.rb path/to/engine/app/models/product.rb Product Saturday, 3 March 12
63. Saturday, 3 March 12
64. ~300 lines of documentation Rails::Engine Saturday, 3 March 12
65. rails plugin new blorgh Saturday, 3 March 12
66. rails plugin new blorgh --full Saturday, 3 March 12
67. rails plugin new blorgh --full --mountable Saturday, 3 March 12
68. A gem by default Saturday, 3 March 12
69. gem ‘blorgh’, :git => ‘git://github.com/radar/blorgh’ Saturday, 3 March 12
70. Step away from the Gemfile Saturday, 3 March 12
71. blorgh.gemspec Saturday, 3 March 12
72. blorgh.gemspec s.add_development_dependency Saturday, 3 March 12
73. blorgh.gemspec s.add_development_dependency s.add_dependency Saturday, 3 March 12
74. lib/blorgh.rb require ‘blorgh/engine’ module Blorgh end Saturday, 3 March 12
75. lib/blorgh/engine.rb module Blorgh class Engine < Rails::Engine end end Saturday, 3 March 12
76. initializer “something” do # your code here end Inside Blorgh::Engine Saturday, 3 March 12
77. Inside Blorgh::Engine config.generators do |g| g.orm :webscale end Saturday, 3 March 12
78. Rails::Application < Rails::Engine Saturday, 3 March 12
79. “In Rails 3.0, a Rails::Application object was introduced which is nothing more than an Engine but with the responsibility of coordinating the whole boot process.” Rails::Application Saturday, 3 March 12
80. Saturday, 3 March 12
81. Inside Blorgh::Engine endpoint SomeRackApp Saturday, 3 March 12
82. Rakefile (tasks go into lib/tasks) Saturday, 3 March 12
83. config initializers locales routes Saturday, 3 March 12
84. Generators Saturday, 3 March 12
85. blorgh:install:migrations Comes standard Saturday, 3 March 12
86. GOOD README not included but for the love of God write one Saturday, 3 March 12
87. The best Rails 3.1 forum system. Saturday, 3 March 12
88. The best Rails 3.1 forum system. Ever. Saturday, 3 March 12
89. Namespacing Namespacing Saturday, 3 March 12
90. rails g model post Saturday, 3 March 12
91. rails g model post app/models/post.rb Saturday, 3 March 12
92. Forem Post App path/to/engine/app/models/post.rb Post Saturday, 3 March 12
93. Forem Post App Post path/to/app/app/models/post.rb path/to/engine/app/models/post.rb Post Saturday, 3 March 12
94. “Just call it something different” Saturday, 3 March 12
95. Yeah. Nah. Saturday, 3 March 12
96. isolate_namespace Forem Saturday, 3 March 12
97. rails g model post Saturday, 3 March 12
98. rails g model post app/models/forem/post.rb Saturday, 3 March 12
99. Forem :: Post App path/to/engine/app/models/forem/post.rb Post Saturday, 3 March 12
100. Forem :: Post App Post path/to/app/app/models/post.rb path/to/engine/app/models/forem/post.rb Post Saturday, 3 March 12
101. forem_posts Saturday, 3 March 12
102. Forem::PostsController forem_posts Saturday, 3 March 12
103. Forem::PostsController app/views/forem/posts forem_posts Saturday, 3 March 12
104. Rails.application.routes.draw Saturday, 3 March 12
105. Rails.application.routes.draw do namespace :forem do resources :forums end end forem/config/routes.rb Saturday, 3 March 12
106. Rails.application.routes.draw Saturday, 3 March 12
107. Forem::Engine.routes.draw Rails.application.routes.draw Saturday, 3 March 12
108. Forem::Engine.routes.draw do resources :forums ... end forem/config/routes.rb Saturday, 3 March 12
109. mount Forem::Engine, :at => “forum” the_app/config/routes.rb Saturday, 3 March 12
110. forums_path /forum/forums Saturday, 3 March 12
111. forums_path forem. /forum/forums Saturday, 3 March 12
112. dropbears_path /dropbears Saturday, 3 March 12
113. dropbears_path main_app. /dropbears Saturday, 3 March 12
114. form_for [forem, @topic, @post] Saturday, 3 March 12
115. form_for [forem, @topic, @post] /forums/topics/1/posts Saturday, 3 March 12
116. Hard Problems Saturday, 3 March 12
117. HOW 2 SHOT AUTH? Saturday, 3 March 12
118. spree_auth Saturday, 3 March 12
119. http://aubenoire.files.wordpress.com/2011/05/not-my-problem.jpg Saturday, 3 March 12
120. class ApplicationController def forem_user current_user end end Saturday, 3 March 12
121. Forem.user_class = “User” config/initializers/forem.rb Into Put Saturday, 3 March 12
122. User#to_s Saturday, 3 March 12
123. Authlogic Saturday, 3 March 12
124. Devise Saturday, 3 March 12
125. Custom Saturday, 3 March 12
126. HOW 2 SHOT AUTH? (part two) Saturday, 3 March 12
127. CanCan CanCan Saturday, 3 March 12
128. <% if can?(:read, category) %> Saturday, 3 March 12
129. Forem::DefaultPermissions Saturday, 3 March 12
130. Forem::DefaultPermissions can_read_forem_forum?(forum) can_read_forem_category?(category) Saturday, 3 March 12
131. can_read_forem_forum?(forum) def true end Saturday, 3 March 12
132. def can_read_forem_forum?(forum) # your code goes here end app/models/user.rb Saturday, 3 March 12
133. module Forem class Ability include CanCan::Ability def initialize(user) user ||= Forem.user_class.constantize.new can :read, Forem::Category do |category| user.can_read_forem_category?(category) end ... Saturday, 3 March 12
134. module Forem class Ability include CanCan::Ability def initialize(user) user ||= Forem.user_class.constantize.new can :read, Forem::Category do |category| user.can_read_forem_category?(category) end ... Saturday, 3 March 12
135. class Forem::ApplicationController def current_ability Forem::Ability.new(forem_user) end ... end Saturday, 3 March 12
136. <% if can?(:read, category) %> Saturday, 3 March 12
137. Theming Saturday, 3 March 12
138. stylesheet_link_tag “forem/theme/twist” app/views/layouts/ forem.html.erb Saturday, 3 March 12
139. module Forem module Theme module Twist class Engine < Rails::Engine end end end end Saturday, 3 March 12
140. Rails::Engine \m/ Saturday, 3 March 12
141. app/assets/stylesheets/ forem/theme/twist.css forem-theme-twist Saturday, 3 March 12
142. app/assets/stylesheets/ forem/theme/twist.css forem-theme-twist javascript + images too! Saturday, 3 March 12
143. Install + Setup Saturday, 3 March 12
144. gem ‘forem’, :git => “git://github.com/radar/forem” Saturday, 3 March 12
145. gem ‘forem’, :git => “git://github.com/radar/forem” bundle install Saturday, 3 March 12
146. gem ‘forem’, :git => “git://github.com/radar/forem” bundle install rake forem:install:migrations Saturday, 3 March 12
147. gem ‘forem’, :git => “git://github.com/radar/forem” bundle install rake forem:install:migrations rake db:migrate Saturday, 3 March 12
148. gem ‘forem’, :git => “git://github.com/radar/forem” bundle install rake forem:install:migrations rake db:migrate create config/initializers/forem.rb Saturday, 3 March 12
149. gem ‘forem’, :git => “git://github.com/radar/forem” bundle install rake forem:install:migrations rake db:migrate create config/initializers/forem.rb Add forem_user method to AppController Saturday, 3 March 12
150. gem ‘forem’, :git => “git://github.com/radar/forem” bundle install rake forem:install:migrations rake db:migrate create config/initializers/forem.rb Add forem_user method to AppController Add User#to_s method Saturday, 3 March 12
151. gem ‘forem’, :git => “git://github.com/radar/forem” bundle install rake forem:install:migrations rake db:migrate create config/initializers/forem.rb Add forem_user method to AppController Add User#to_s method Go into console + create first forum Saturday, 3 March 12
152. gem ‘forem’, :git => “git://github.com/radar/forem” bundle install rake forem:install:migrations rake db:migrate create config/initializers/forem.rb Add forem_user method to AppController Add User#to_s method Go into console + create first forum Mount Forem::Engine, :at => ‘/’ Saturday, 3 March 12
153. gem ‘forem’, :git => “git://github.com/radar/forem” bundle install rake forem:install:migrations rake db:migrate Pray that it works. create config/initializers/forem.rb Add forem_user method to AppController Add User#to_s method Go into console + create first forum Mount Forem::Engine, :at => ‘/’ Saturday, 3 March 12
154. gem ‘forem’, :git => “git://github.com/radar/forem” Saturday, 3 March 12
155. gem ‘forem’, :git => “git://github.com/radar/forem” bundle install Saturday, 3 March 12
156. gem ‘forem’, :git => “git://github.com/radar/forem” bundle install rails g forem:install Saturday, 3 March 12
157. gem ‘forem’, :git => “git://github.com/radar/forem” bundle install rails g forem:install Answer two questions. Saturday, 3 March 12
158. gem ‘forem’, :git => “git://github.com/radar/forem” bundle install rails g forem:install It works! Answer two questions. (assuming you have a User model) Saturday, 3 March 12
159. Spree 1.0 Saturday, 3 March 12
160. Namespace everything Saturday, 3 March 12
161. SpreeCore Saturday, 3 March 12
162. Spree::Core Spree::Auth Saturday, 3 March 12
163. Spree ::Core::Product Saturday, 3 March 12
164. Spree ::Product Saturday, 3 March 12
165. Spree:: Product App Product path/to/app/app/models/product.rb path/to/engine/app/models/spree/product.rb Product Saturday, 3 March 12
166. Spree:: Product App Product path/to/app/app/models/product.rb path/to/engine/app/models/spree/product.rb Product Saturday, 3 March 12
167. Forem Forem Saturday, 3 March 12
168. Forem App Forem Saturday, 3 March 12
169. Forem::Engine.routes.draw Saturday, 3 March 12
170. mount Forem::Engine, :at => “forums” Saturday, 3 March 12
171. Core Auth API Promo Dash Spree Saturday, 3 March 12
172. Core Auth API Promo Dash App Spree Saturday, 3 March 12
173. Spree::Core::Engine.routes.draw Spree::Auth::Engine.routes.draw Spree::Promo::Engine.routes.draw Spree::Dash::Engine.routes.draw Spree::Api::Engine.routes.draw Saturday, 3 March 12
174. mount Spree::Core::Engine, :at => ‘/’ mount Spree::Auth::Engine, :at => ‘/’ mount Spree::Api::Engine, :at => ‘/’ mount Spree::Dash::Engine, :at => ‘/’ mount Spree::Promo::Engine, :at => ‘/’ Saturday, 3 March 12
175. mount Spree::Core::Engine, :at => ‘/’ mount Spree::Auth::Engine, :at => ‘/’ mount Spree::Api::Engine, :at => ‘/’ mount Spree::Dash::Engine, :at => ‘/’ mount Spree::Promo::Engine, :at => ‘/’ mount Spree::YourExtension, :at => ‘/’ mount Spree::YourExtension, :at => ‘/’ mount Spree::YourExtension, :at => ‘/’ mount Spree::YourExtension, :at => ‘/’ Saturday, 3 March 12
176. spree_core.root_path spree_auth.login_path Saturday, 3 March 12
177. HAHAHAHAHAHAHAHAHAH AHAHAHAHAHAHAHAHAHA HAHAHAHAHAHAHAHAHAH AHAHAHAHAHAHAHAHAHA HAHAHAHAHAHAHAHAHAH AHAHAHAHAHAHAHAHAHA HAHAHAHAHAHAHAHAHAH AHAHAHAHAHAHAHAHAHA HAHAHAHAHAHAHAHAHAH AHAHAHAHAHAHAHAHAHA HAHAHAHAHAHAHAHAHAH Saturday, 3 March 12
178. mount Spree::Core::Engine, :at => ‘/’ Saturday, 3 March 12
179. spree.login_path spree.root_path Saturday, 3 March 12
180. Spree::Core::Engine.routes.prepend Saturday, 3 March 12
181. Spree::Core::Engine.routes.prepend do mount Spree::Auth::Engine, :as => “spree” end Saturday, 3 March 12
182. Core Auth API Promo Dash App Extensions Saturday, 3 March 12
183. Core Auth API Promo Dash App Extensions Saturday, 3 March 12
184. Fix everything Saturday, 3 March 12
185. describe Spree::ProductsController do it “gets a list of products” do get :index end end spec/controllers/products_controller_spec.rb Saturday, 3 March 12
186. describe Spree::ProductsController do it “gets a list of products” do get :index end end spec/controllers/products_controller_spec.rb No route matches { :controller => “Spree::ProductsController”, :action => “index” } Saturday, 3 March 12
187. Saturday, 3 March 12
188. http://stackoverflow.com/a/5832908/15245 How do I write a Rails 3.1 engine controller test in RSpec? The workaround is quite simple, instead of this get  :show,  :id  =>  1 use this get  :show,  {:id  =>  1,  :use_route  =>  :posts} Saturday, 3 March 12
189. Well, duh. Saturday, 3 March 12
190. :use_route  =>  :spree Saturday, 3 March 12
191. Saturday, 3 March 12
192. rails-3.1 (3-1-stable)♐ ack ":use_route" actionpack/lib/action_dispatch/routing/route_set.rb actionpack/test/controller/routing_test.rb actionpack/test/template/form_helper_test.rb Saturday, 3 March 12
193. rails-3.1 (3-1-stable)♐ ack ":use_route" actionpack/lib/action_dispatch/routing/route_set.rb actionpack/test/controller/routing_test.rb actionpack/test/template/form_helper_test.rb Three files. No comments. No description. Saturday, 3 March 12
194. Saturday, 3 March 12
195. Magic. Saturday, 3 March 12
196. Fixed everything Saturday, 3 March 12
197. Bug fixes too! (thanks!) Saturday, 3 March 12
198. Spree 1.0 is the now Saturday, 3 March 12
199. Use it. (Please) Saturday, 3 March 12
200. One more thing... Saturday, 3 March 12
201. I lied to you. I’m sorry. Saturday, 3 March 12
202. Really. Really. Saturday, 3 March 12
203. Saturday, 3 March 12
204. Enjoy. Enjoy. Saturday, 3 March 12
205. Enjoy. Enjoy. Thanks! Saturday, 3 March 12