title: Identifying which fields have changed before CoreData saves
body: <p>//set up notifications</p>
  
  <pre><code>[[NSNotificationCenter defaultCenter]
   addObserver:self
   selector:@selector(dataChanged:)
   name:NSManagedObjectContextDidSaveNotification
   object:context];    
  </code></pre>
  
  <p>//later</p>
  
  <pre><code>- (void)dataChanged:(NSNotification *)notification{
    NSDictionary *info = notification.userInfo;
    NSSet *insertedObjects = [info objectForKey:NSInsertedObjectsKey];
    NSSet *deletedObjects = [info objectForKey:NSDeletedObjectsKey];
    NSSet *updatedObjects = [info objectForKey:NSUpdatedObjectsKey];
  </code></pre>
  
  <p>Is there anyway to determine from the updatedObjects which fields were actually changed?</p>
  
  <p>thanks,
  Michael</p>