Rails Engine is a pre-packaged Ruby on Rails application that can be mounted within another Rails application to provide reusable functionality, it allows extracting common features into modules or gems that integrate with a Rails application using Railties, and some examples of Rails Engines include Devise for authentication and Rails Admin for administration.

1. Rails Engine
An awesome tool to extend your rails application
Muntasim Ahmed
Platform Architect @ Tasawr Interactive
https://github.com/railscash
muntasim@tasawr.com

2. Agenda
• Why Rails Engine
• What is Rails Engine
• How it works with Rails Core
• Who are they
• Where is your interest

3. Problems
• Large application without reusable component
• Slow testing ( if any :) )
• Larger app, messy

4. Solution
• Find common functionalities
• Extract them to module => Gems
• Use railtie to tie with Rails App => Rails Engine

5. One Thing!
Rails (version>=3.1) is just a “supercharged” engine
http://edgeguides.rubyonrails.org/engines.html

6. Rails Engine ?
• pre-packaged application
• able to be run or mounted within another Rails
application
• can have its own models, views, controllers,
generators and publicly served static files

7. Rails Engine ?
•

8. Rails Engine has
Image source: Railscasts.com

9. Rails Engine has
Image source: Google

10. Rails Engine has
Image source: Google

11. Rails Engine has
Image source: Google

12. Rails engine walk-through
• Create an engine
• Implement requirements in app, lib etc.
• Test
• Mount to main app
• Override where necessary
• And done!

13. Rails engine walk-through
Create
rails plugin new awesome_engine --mountable
Then generate mvc stuffs, test
In App Gemfile
gem "awesome_engine", path => "awesome_engine_path
In App Route
mount AwesomeEngine::Engine => "/awesome_engine_path", as =>
“awesome_engine"

14. Rails engine walk-through
Hit localhost:3000/awesome_engine_path
(mount point)
It will hit engine's root path
Welcome to awesome engine
home!

15. Rails engine walk-through
Routes:
Use engine routes from main app using
engine_name.route_name
e.g. awesome_name.root_path

16. Rails engine walk-through
Routes:
Use main app routes from engine using
main_app.route_name
e.g. main_app.root_path

17. Who are they
• Rails Admin
• Devise
• Blogit
• Tolk
• .....

18. References
• http://railscasts.com/episodes/277-mountable-engines
• http://www.slideshare.net/AndyMaleh/rails-engine-patterns
• http://www.slideshare.net/mirrec/rails-engine-rubyslava
• http://edgeguides.rubyonrails.org/engines.html
• http://edgeapi.rubyonrails.org/classes/Rails/Engine.html
• http://pivotallabs.com/users/shagemann/blog/articles/1994-
migrating-rom-a-single-rails-app-to-a-suite-of-rails-engines
Image source:
Google, Railscasts and Dulal Khan

19. Thanks for your attention :)

20. ???
Question(s)