Module included

action_controller.rb

class UserDefined
  module ActionController # :nodoc: all
    def self.included(base)
      base.send :helper_method, :user_method
    end

    private
    def user_method
      @user_defined ||= UserDefined.new(
        :var => 'value',
        :variable => 'variable'
      )
    end
  end
end

ActionController::Base.send :include, UserDefined::ActionController

user_defined.rb

class UserDefined
  # Add Rails helper if ActionController::Base is defined
  require "folder/action_controller" if defined?(ActionController::Base)
end