Extending controllers of a Rails 3 Engine in the main app

Question

I am using a Rails engine as a gem in my app. The engine has PostsController with a number of methods and I would like to extend the controller logic in my main

Answer 1

Method 1

Here is what I put in my Rails 3 app in application.rb after require 'rails/all' (let me know if it is a bad place to put it)

require 'active_support/dependencies'
module ActiveSupport::Dependencies
  alias_method :require_or_load_without_multiple, :require_or_load
  def require_or_load(file_name, const_path = nil)
    if file_name.starts_with?(Rails.root.to_s + '/app')
      relative_name = file_name.gsub(Rails.root.to_s, '')
      #@engine_paths ||= Rails::Application.railties.engines.collect{|engine| engine.config.root.to_s }
      #EDIT: above line gives deprecation notice in Rails 3 (although it works in Rails 2), causing error in test env.  Change to:
      @engine_paths ||= YourAppName::Application.railties.engines.collect{|engine| engine.config.root.to_s }
      @engine_paths.each do |path|
        engine_file = File.join(path, relative_name)
        require_or_load_without_multiple(engine_file, const_path) if File.file?(engine_file)
      end
    end
    require_or_load_without_multiple(file_name, const_path)
  end
end

For a while this didn't work raising

TypeError in PostsController#index

superclass mismatch for class PostsController

but that was due to a mistyped class definition class PostsController < ActionController::Base which should be class PostsController < ApplicationController

Method 2

If you do not want to do this for all engine controllers etc., you can load the engine's controller before the definition in the main app

require PostsEngine::Engine.config.root + 'app' + 'controllers' + 'posts_controller'

class PostsController < ApplicationController
  # extended methods
end