Ruby on Rails and Rails Engine

Question

Can I access main app's ApplicationController in my rails engine? I want to apply a filter to my app's ApplicationController through an engine. A bit of code will be really helpful.

Thanks!

Answer 1

You can always, in your engine, open the ApplicationController and write whatever filter you want. This will be used by your main app automatically after the engine has been loaded.

Example code in your engine for a set_locale before_filter :

class ApplicationController < ActionController::Base
  before_filter :set_locale

  def set_locale
    I18n.locale = params[:locale] if params[:locale].present?
  end
end

Answer 2

You could isolate the functionality with which you wish to enhance your host application's ApplicationController doing the following:

1. Create a controller concern having the filter method.

Create app/controllers/concerns/filterable.rb

module Concerns::Filterable
  include ActiveSupport::Concern

  included do
    before_filter :do_something
  end

  module InstanceMethods
    def do_something
    end
  end
end

Create config/initializers/filterable.rb

Rails.application.config.to_prepare do
  ApplicationController.send :include, Concerns::Filterable if defined ApplicationController
end

Using the initializer above, we make sure our Concerns::Filterable is included every time the application is reloaded in development.