title: UICollectionView scroll to last item without Animation
body: <p>I have a UICollectionView to display chat messages. At the beginning I load the existing messages to the collectionView and scroll the collectionView down to the last message with this method:</p>
  
  <pre><code>- (void)scrollToLastMessageAnimated:(BOOL)animated;
  {
      if (_messages.count == 0) { return; }
  
      NSUInteger indexOfLastSection = _messagesBySections.count - 1;
      NSInteger indexOfMessageInLastSection = [_messagesBySections[indexOfLastSection] count] - 1;
      NSIndexPath *path = [NSIndexPath indexPathForItem:indexOfMessageInLastSection
                                              inSection:indexOfLastSection];
  
      [_collectionView scrollToItemAtIndexPath:path
                             atScrollPosition:UICollectionViewScrollPositionCenteredVertically
                                     animated:animated];
  }
  </code></pre>
  
  <p>This only works animated when I call it in the viewDidAppear: method and not in viewWillAppear: method. How can I scroll down without animation?</p>