Recently I have been porting an app into Rails 3 and probably you have also been poking this new Rails 3 with ruby 1.9.2. Therefore I would like to discuss a bit more about Rails 3 itself. Particularly, things under railties lib directory covering classes such as Railtie, Engine, Application and will go through initialization with initializers. Along the way I'll show some examples how you can use this knowledge in your own gem or plugin. Nothing too fancy but should be useful for developing your next Rails

1. If you like go a bit more in depth,
please read Piotr Sarnacki article:
http://piotrsarnacki.com/2010/06/18/rails-internals-railties/
Anyhow, here is my slides for meetup.

2. Poke into Rails 3 railites
Priit Tamboom
priit@gitnation.com
London
13.09.2010

3. puts 'Hello!'
Early days...
Not so early days...
Recent days...
...or just short shameless self presentation.

4. Presentation is about:
Railtie and it's responsibilty
Engine and Application classes
Initialization
...and one more thing ;-)

5. Credits and thanks goes to:
Rails 3 source code
Rails 3 edge guides
José Valim and other Devise developers
Piotr Sarnacki and his summer work/blog
http://piotrsarnacki.com
Own experience during summer in Barcelona

6. What's the responsibility of Railites:
Glues all together
Handles all bootstrapping process
Provides rails command line interface
Provides rails generators core

7. What about class Railtie?
railties/lib/rails/railtie.rb
Class Railtie is the core of the Rails Framework
and provides several hooks to extend Rails and/or
modify the initialization process.

8. Creating your own Railtie
# APP/Gemfile
gem 'my_gem'
# GEM/lib/my_gem.rb
requrie 'my_gem/railtie' if defined?(Rails)
# GEM/lib/my_gem/railtie.rb
module MyGem
class Railtie < Rails::Railtie
end
end

9. What about Engine class?
First, don't get confused with Engine plugin.
Rails 3 Engine class is quite different thing.

10. Engine is just subclass of Railtie
# railties/lib/rails/engine.rb
module Rails
class Engine < Railtie
end
end

11. Available paths in an Engine
class MyEngine < Rails::Engine
paths.app = "app"
paths.app.controllers = "app/controllers"
paths.app.helpers = "app/helpers"
paths.app.models = "app/models"
paths.app.views = "app/views"
paths.lib = "lib"
paths.lib.tasks = "lib/tasks"
paths.config = "config"
paths.config.initializers = "config/initializers"
paths.config.locales = "config/locales"
paths.config.routes = "config/routes.rb"
end

12. Use middleware in initialization
# lib/my_gem/railtie.rb
class MyRailtie < Rails::Railtie
initializer "my_railtie.initialization" do |app|
app.middleware.use MyRailtie::Middleware
end
end

13. One more thing :-)

14. What to expect from Rails 3.1?

15. What, not excited?

16. Anyhow, heavy lifting done by Piotr Sarnacki in
his time with Ruby Summer of Code.
At the moment treat his work as any other Rails
edge code, I'm sure he welcomes any feedback.

17. What to expect from Rails 3.1?
* Engine is now rack application
* Added middleware stack to Engine
* Engine can now load plugins
* Engine can load its own environment file
* Added helpers to call engines' route helpers
from application and vice versa

18. What to expect from Rails 3.1?
* Task for copying plugins' and engines'
migrations to application's db/migrate directory
* Changed ActionDispatch::Static to allow
handling multiple directories
* Added namespace() method to Engine, which
sets Engine as isolated
* Include all helpers from plugins and shared
engines in application

19. Good news
It looks Rails 3.1 will probably be very friendly for
multible/mountable apps.

20. Bad news
Please, don't go crazy with mountable apps,
even with Rails 3.1
In my reality it's a pipe dream to create and use
very high level dependencies.

21. However there is nish
Take a look how Devise works and what kind
workflow/attitude José Valim has.
He has given a nice introduction about this topic in Barcelona,
probably there will be something on online as well.

22. Thank you for you time!
Any questions or comments?
Just in case, here is my profiles:
Github.com/priit
Twitter.com/priit
http://priit.mx.ee
priit@gitnation.com