How can I extend ApplicationController in a gem?

Question

I thought I\'d come up with a slick way to extend ApplicationController in a Rails 3.x gem.

In my gem\'s lib/my_namespace/my_controller.rb, I had:

Answer 1

I was able to reference ApplicationController with an initializer callback.

gem code that subclasses/references ApplicationController:

class GemApplicationController < ApplicationController
  before_filter :method_to_call

  def method_to_call
    #your code here
  end
end

gem code callback to create subclassed controller:

module GemName
  def self.load_gem_application_controller
    require "path/to/gem_application_controller"
  end
end

rails_app/config/initializers/gem_name.rb

GemName.load_gem_application_controller

Then have controllers that use this functionality subclass GemApplicationController

class SpecialCaseController < GemApplicationController
  # this will inherit from the gem's controller, 
  # which inherits from the rails_app ApplicationController
end

Answer 2

Here is a Gist that shows how to access the class of the subclass and store it in an instance variable and access it in the before and after filters. It uses the include method.

Answer 3

For this specific kind of functionality I would recommend creating a module in your gem and include that module in your Application Controller

class ApplicationController < ActionController::Base
  include MyCoolModule
end

To add before filters, etc (add this to your module)

def self.included(base)
  base.send(:before_filter, my_method)
end

Update: you may be able to just do base.before_filter :my_method which is cleaner.

Answer 4

Truth is much much simpler and flexible.

Add to lib/engine.rb this: class Engine < Rails::Engine; end

And then simply use:

ActionController::Base.class_eval do

  include SomethingFromMineGemModule

  # or:
  def hello_from_gem
    'Hey people!'
  end

end