How to call a parent app's helper method from a rails 3.1 engine

Question

I'm building a rails engine that uses the "acts as" format to establish relationships with the parent application's User model.

module Cornerstone

  module ActsAsCornerstoneUser

    extend ActiveSupport::Concern

    module ClassMethods

      def acts_as_cornerstone_user(options = {})

        #= Associations
        has_many :cornerstone_discussions


        #= Options
        Cornerstone::Config.auth_with << options[:auth_with] if options[:auth_with]
        Cornerstone::Config.auth_with.flatten!

      end
    end

    module InstanceMethods

    end

  end

  ActiveRecord::Base.send :include, ActsAsCornerstoneUser

end

I would like for a developer to be able to specify a helper method name using the :auth_with option. The idea is that the developer will specify a helper method in the parent application that will return the signed in user for that session.

My question is once the developer has specified the auth_with option, how can I call that parent application's method??

Is there a better approach to obtaining the parent application's signed in user? I'd like it to be as flexible as possible such that it is not dependent on simply calling current_user.

Answer 1

Something like this should work, as long as you have only one cornerstone user defined in your application :

module Cornerstone
  module ActsAsCornerstoneUser
    extend ActiveSupport::Concern

    module ClassMethods
      def acts_as_cornerstone_user(options = {})

        #= Associations
        has_many :cornerstone_discussions

        #= Options
        Cornerstone::Config.auth_with = options[:auth_with] if options[:auth_with]
      end
    end

    module InstanceMethods

    end

    def self.included(base)
      base.extend(ClassMethods)
      base.include(InstanceMethods)
    end
  end

  ActiveRecord::Base.send :include, ActsAsCornerstoneUser
end

Then define a helper in your gem (ie. in app/helpers/cornerstone_helper.rb) :

module Cornerstone
  module CornerStoneHelper
    def current_cornerstone_user
      Config.auth_with.call(controller)
    end
  end
end

The acts_as_cornerstone method is the used like this :

class MyUser < ActiveRecord::Base
  acts_as_cornerstone_user :auth_with => Proc.new { |controller| controller.current_user }
end

You can then use the current_cornerstone_user helper to get the current authenticated user.

This method breaks when acts_as_cornerstone_user is used on multiple classes. But you then have the problem of having multiple cornerstone users without knowing anything about the application models (you're supposed to be in your gem).

Update

If you'd like to have a syntax like :auth_with => :warden, you could replace the helper with the following :

module Cornerstone
  module CornerStoneHelper
    def current_cornerstone_user
      if Config.auth_with.respond_to?(:call)
        Config.auth_with.call(controller)
      elsif Config::AUTH_MODES.keys.include?(Config.auth_with)
        Config::AUTH_MODES[Config.auth_with].call(controller)
      end
    end
  end
end

with Cornerstone::Config::AUTH_MODES set up like this :

module Cornerstone
  class Config
    AUTH_MODES = {
      :warden => Proc.new { |controller| controller.env['warden'].user },
      :devise => Proc.new { |controller| controller.current_user }
    }
  end
end