title: Subclassing ActiveRecord with permalink_fu in a rails engine
body: <p>This question is related to extending class methods in Ruby, perhaps more specifically in the way that permalink_fu does so.</p>
  
  <p>It appears that <code>has_permalink</code> on a model will not be available in a derived model. Certainly I would expect anything defined in a class to be inherited by its derived classes.</p>
  
  <pre><code>class MyScope::MyClass &lt; ActiveRecord::Base
    unloadable
    self.abstract_class = true
    has_permalink :name
  end
  
  class MyClass &lt; MyScope::MyClass
    unloadable
    #has_permalink :name # This seems to be required
  end
  </code></pre>
  
  <p>Is there something in the way permalink_fu mixes itself in that causes this issue?</p>
  
  <p>I'm using the permalink-v.1.0.0 gem <a href="http://github.com/goncalossilva/permalink_fu" rel="nofollow noreferrer">http://github.com/goncalossilva/permalink_fu</a></p>