Creating Mountable Engines

With Rails 4.0 killing off the humble plugin, there is never a better time to learn how to create reusable code using Engines. Creating an engine can be as simple as adding a model, or a complex as an entire content management system. Using the Asset Pipeline, even javascript and css files can be packaged and shared, making projects cleaner and more maintainable than ever before.

This talk will cover how developers can create their own engines, to add new controllers/models/views, rake tasks and/or generators. It will cover how engines can interact with Rails having their own initializers and middleware. Finally, based on our experiences converting BrowserCMS and its entire module ecosystem to work as mountable engines, this talk will cover how to make engines that are designed to work together, extend each other engine’s behavior and make it easy for developers to upgrade when you release new versions.

Transcript

1. Creating Mountable Engines Patrick Peak @peakpg
2. About me
3. Problem: Repeating yourself is easy
4. Duplication is the root of all evil.
5. Start with a library
6. Plugins are dead
7. Generated code makes upgrades costly
8. Engines are the solution
9. Agenda Agenda • - Why I care • - How to make one • - Things you can do • - Working with others
10. Evolving a CMS with engines Evolution of a CMS 3.0 Engines Introduced 3.1 -Mountable -Initializers -Asset Pipeline 4.0 2.3 Gems over plugins
11. What are engines? What are Engines? Responsibilities: •  Business Domain •  Selling Stuff •  Managing Users •  Blogging App #2 ?
12. Separation of concerns Separation of Concerns Selling Stuff Managing Users Blogging Business Domain App #2
13. Examples Popular engines
14. E-commerce
15. Authentication
16. Admin dashboards
17. Building an Engine
18. Creating an engine What the world needs… $ rails plugin new rubypress --mountable
19. Result: A gem with a rails app inside Gemspec Rails App
20. Add a resource Add a Resource $ rails g resource Page name path content
21. The ‘expected’ controller ‘Typical’ Controller
22. An isolated controller
23. Isolated Namespace Defining an isolated namespace
24. Routing Engines own their routes
25. Multiple buckets of controllers Application Engine #2 Engine #1
26. Engine routes Engine Routes Rails.application.routes.draw
27. Calling resources http://localhost:3000/rubypress/pages
28. Mounting the engine App Root
29. Route helpers Route Helpers <%= main_app.root_url %> # => / <%= rubypress.root_url %> # => /rubypress <%= rubypress.page_path(@page) %> # => /rubypress/pages/1
30. Getting smart about your routes
31. A view from inside the engine
32. Views inside your application
33. An engine by any other name…
34. Would be just as redundant
35. Migrations Sharing structure across projects
36. Namespaced tables Namespaced Tables
37. Out of the gem, into the project From Gem to Project $ rake rubypress:install:migrations - Copies from gem’s db/migrate into a project - Won’t overwrite existing
38. After installing 2 1 ####_create_rubypress_pages.rubypress.rb
39. Installing migrations for all engines For multiple engines $ rake railties:install:migrations
40. Configuration Provide reasonable defaults
41. http://edgeguides.rubyonrails.org/configuring.html
42. Initializers Initializers
43. Extending rails behavior
44. Using new DSL
45. Middleware stack
46. “Suggested” generators “Suggested” Generators
47. Make your engine configurable
48. Overriding default configuration
49. Be Nice Make life easy for new users
50. Write a README Write a Readme gem "rubypress" $ bundle install $ rake rubypress:install:migrations $ rake db:migrate mount Rubypress::Engine=>"/rubypress"
51. Improve installation Improve Installation gem "rubypress" $ rail g rubypress:install
52. Generators Generators
53. Asset Pipeline Packaging the view
54. Before 3.1 /public $ rake rubypress:copy_assets
55. After 3.1 Project gem "ckeditor_rails", "3.6.2.2"
56. My favorite key
57. Working Together Ups and downs of multiple engines
58. Common stacks are easier My Site BrowerCMS News Blog
59. Allows for established conventions Establishing Conventions $ rails g cms:install bcms_news
60. A common installer
61. The Holy Grail for engine ecosystem The vision Your Engine Rails Admin
62. Challenges on our quest Challenges A. Incompatible dependencies B. Rails has no common security model C. Mismatched user interfaces
63. A. Incompatible dependencies Devise =2.1.1 ~>2.0.0 Rails Admin
64. Managing your engine dependencies Solving Dependencies - Minimize dependencies - Be Rational: Major.Minor.Build (i.e. 3.5.4) - Major – Backwards incompatible - Minor – New features - Build – Details - Robustness Principle: - Be liberal in what you accept - ~> 2.0 better than ~>2.0.0
65. B. No common security model Your App Restful Auth Devise current_user?
66. Authentication Who are you, really?
67. Authorization Are you allowed to do that?
68. I don’t care which, just pick one…
69. C. Mismatched UIs
70. Recap What I hope you learned
71. Engines are the future, and awesome.
72. Reduce errors from duplication
73. When done right…
74. The End Thanks!
75. Attributions http://dilbert.com/strips/comic/2009-12-03/ http://trevorlibrarian.wordpress.com/2012/04/04/safety-first/ http://www.flickr.com/photos/jowo/95371566/sizes/o/in/photostream/ http://www.flickr.com/photos/rosenfeldmedia/4459977458/sizes/o/in/photostream/ https://www.ruby-toolbox.com/ http://www.flickr.com/photos/7571290@N05/440978769/sizes/m/in/photostream/ http://www.spreecommerce.com http://www.flickr.com/photos/verseguru/168920451/sizes/o/in/photostream/ http://www.flickr.com/photos/richardgiles/5284155911/sizes/o/in/photostream/ http://www.flickr.com/photos/museemccordmuseum/2918567169/sizes/o/in/photostream/ http://www.flickr.com/photos/whisperwolf/4487007569/
76. Questions?