title: Rails 4, record not-persisted in after create callback & Delayed Job
body: <p>I've a really expensive method to run after creating an instance of a 'Klass', so I want to queue the job in DelayedJob. </p>
  
  <pre><code>class Klass
    has_many :klass_instances
    after_create :create_klassinstances
  
    def create_klassinstances
      .....
      delay.create_if_ok_to_create_klass_instances
      .....
    end
  
  end 
  </code></pre>
  
  <p>However this throws the error </p>
  
  <pre><code>#&lt;ArgumentError: job cannot be created for non-persisted record:
  </code></pre>
  
  <p>Which I don't really understand. I am using an 'after_create' call back so surely an ID must exist now for the Klass record? I've played around with pry and calling 'self' in the create_klassinstances method returns the non persisted object with the ID set as nil. </p>