title: Why am I not able to override isEqual in my NSManagedObject subclass?
body: <p>I have two custom <code>NSManagedObject</code> classes: <code>Notes</code> and <code>Tags</code>.</p>
  
  <p>When I override the <code>isEqual:</code> function in the <code>Tags</code> class I get an error message like this:</p>
  
  <blockquote>
    <p>'Class 'Tags' for entity 'Tags' has an illegal override of NSManagedObject -isEqual:'</p>
  </blockquote>
  
  <p>Why is this happening?</p>