Rails engines extending functionality

Question

I have an engine which defines some models and controllers. I want to be able to extend functionality of some models/controllers in my application (eg. adding methods) witho

Answer 1

You can add these lines to you engine's module file in the lib root directory:

def self.root
  File.expand_path(File.dirname(File.dirname(__FILE__)))
end

def self.models_dir
  "#{root}/app/models"
end

def self.controllers_dir
  "#{root}/app/controllers"
end

Then you have the ability in the main application (the app making use of the engine) to require the necessary files from the engine. This is nice because you maintain Rails Engines default functionality and also have an easy tool for making use of normal ruby inheritance, without the need for patching.

EX:

#ENGINE Model -

class User < ActiveRecord::Base
  def testing_engine
    puts "Engine Method"  
  end
end

#MAIN APP Model -

require "#{MyEngine.models_dir}/user"
class User
  def testing_main_app
    puts "Main App Method"  
  end
end

#From the Main apps console

user = User.new

puts user.testing_engine #=>  "Engine Method"

puts user.tesing_main_app #=> "Main App Method"