title: Core-Data willSave: method
body: <p>I have an attribute <code>modificationDate</code> in my <code>Entity A.</code> I want to set its value whenever <code>NSManagedObject</code> is saved. However, if i try to do that in <code>NSManagedObject</code> <code>willSave:</code> method, i get an error:</p>
  
  <pre><code>*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Failed to process pending changes before save.  The context is still dirty after 100 attempts.  Typically this recursive dirtying is caused by a bad validation method, -willSave, or notification handler.' ***
  </code></pre>
  
  <p>So, i'm wondering, what's the best way to set the value of <code>modificationDate</code>?</p>