title: UICollectionView animate data change
body: <p>In my Project I use UICollectionView to display a grid of icons.</p>
  
  <p>The user is able to change the ordering by clicking a segmented control which calling a fetch from core data with different NSSortDescriptor. </p>
  
  <p><strong>The amount of data is always the same, just ending up in different sections / rows:</strong></p>
  
  <pre><code>- (IBAction)sortSegmentedControlChanged:(id)sender {
  
     _fetchedResultsController = nil;
     _fetchedResultsController = [self newFetchResultsControllerForSort];
  
     NSError *error;
     if (![self.fetchedResultsController performFetch:&amp;error]) {
         NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
     }
  
     [self.collectionView reloadData];
  }
  </code></pre>
  
  <p>The problem is that reloadData doesn't animate the change, UICollectionView just pops with the new data.</p>
  
  <p>Should I keep track in which indexPath a cell was before and after change, and use [self.collectionView moveItemAtIndexPath: toIndexPath:] to perform the animation for the change or there is a better method ?</p>
  
  <p>I didn't get much into subclassing collectionViews so any help will be great... </p>
  
  <p>Thanks,
  Bill.</p>