Introduction to Rails Engines

1. Rails::Engine
@flaviamissi
flaviamissi.com.br

2. What is a engine?
<<
slices
engine

3. What is a engine?
●
Works exactly as a built-in rails application
●
Railtie
●
Active Record
●
Active Resource
●
Action Mailer
●
Action Controller
●
Action View

4. Application -> Engine -> Railtie
module Rails
class Application < Engine
...
class Engine < Railtie
...
...
https://github.com/rails/rails/blob/master/railties/lib/rails/application.rb
https://github.com/rails/rails/blob/master/railties/lib/rails/engine.rb

5. http://www.flickr.com/photos/imelda/1022089050/sizes/l/in/photostream/

6. Creating Our Engine App
$ rails new MyApp

7. What you don't need
$ rm -rf log/
$ rm -rf tmp/
$ rm -rf doc/
$ rm -rf vendor/
$ rm -rf config/enviroments/
$ rm -rf config/initializers/ *
$ rm -rf config/boot.rb *
$ rm -rf script/ *
* = later!

8. And We Have Now...

9. A Simple Blog App
$ rails g scaffold Blog::Post title:string post:text
namespace!

10. routes.rb
Engine::Application.routes.draw do
Rails.application.routes.draw do

11. config/application.rb
module MyApp
class Application < Rails::Application
module MyApp
class Engine < Rails::Engine

12. Integrating With Another App
$ cp -R ~/my_engine ~/my_app/vendor/plugins/

13. Integrating With Another App
$ rake routes
blog_posts GET /blog/posts(.:format) {:action=>"index", :controller=>"blog/posts"}
POST /blog/posts(.:format) {:action=>"create",
:controller=>"blog/posts"}
new_blog_post GET /blog/posts/new(.:format) {:action=>"new", :controller=>"blog/posts"}
edit_blog_post GET /blog/posts/:id/edit(.:format) {:action=>"edit", :controller=>"blog/posts"}
blog_post GET /blog/posts/:id(.:format) {:action=>"show",
:controller=>"blog/posts"}
PUT /blog/posts/:id(.:format) {:action=>"update",
:controller=>"blog/posts"}
DELETE /blog/posts/:id(.:format) {:action=>"destroy",
:controller=>"blog/posts"}

14. Só isso?!
http://www.flickr.com/photos/bee721/5784266118/

15. A Problem...
Migrations and everything inside public/
are not available to the main application

16. The Solution
namespace :engine do
task :create, :engine do |cmd, args|
puts "Creating symbolic links..."
system "mkdir #{Rails.root.to_s}/public/#{args[:engin
system "ln -s #{Rails.root.to_s}/vendor/plugins/#{arg
system "ln -s #{Rails.root.to_s}/vendor/plugins/#{arg
puts "Done!"
end
end

17. Some Interesting Links
●
https://github.com/search?q=rack&type=Everything&repo=&langOverride=&start_
●
http://akitaonrails.com/2010/05/10/rails-3-introducao-a-engines
●
http://api.rubyonrails.org/classes/Rails/Engine.html
●
http://api.rubyonrails.org/classes/Rails/Railtie.html