inviter.rb

module Invite
  module Inviter

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

    module ClassMethods
      attr_reader :invite_block

      def acts_as_inviter(&block)
        @invite_block = block
      end
    end
    
    def approve!(user)
      self.class.invite_block.call user
    end    
  end
end