title: UIView transform property is being reset
body: <p>I have a UICollectionView. I want a behaviour where when the user touches a cell, it scales down, as if it is getting pushed down slightly. I've accomplished this by using the UICollectionViewDelegate methods:</p>
  
  <pre><code>- (void)collectionView:(UICollectionView *)collectionView didHighlightItemAtIndexPath:(NSIndexPath *)indexPath
  {
      UICollectionViewCell *cell = [collectionView cellForItemAtIndexPath:indexPath];
      [self scaleDownCell:cell];
  }
  
  - (void) collectionView:(UICollectionView *)collectionView didUnhighlightItemAtIndexPath:(NSIndexPath *)indexPath{
      UICollectionViewCell *cell = [collectionView cellForItemAtIndexPath:indexPath];
      [self scaleUpCell:cell];
  }
  </code></pre>
  
  <p>My problem is that sometimes my cell will start to scale down, and then suddenly go back to full size, without performing the scale up animation, creating jerky effect. I have checked with breakpoints that it scales up before my scale up method is called. I am trying to figure out why.</p>
  
  <p>The scale functions are as follows:</p>
  
  <pre><code>+ (void)scaleDownCell:(UICollectionViewCell *)cell
  {
      CGAffineTransform transform = CGAffineTransformMakeScale(0.95, 0.95);    
      [UIView animateWithDuration:SCALE_DOWN_ANIMATION_DURATION
                            delay:0.0
           usingSpringWithDamping:SCALE_DOWN_SPRING_DAMPING
            initialSpringVelocity:SCALE_DOWN_SPRING_VELOCITY
                          options:0
                       animations:^{
                           cell.transform = transform;
                       }
                       completion:^(BOOL finished) {
                       }];
  }
  
  + (void)scaleUpCell:(UBCollectionViewCell *)cell
  {
      CGAffineTransform transform = CGAffineTransformMakeScale(1.0, 1.0);    
      [UIView animateWithDuration:SCALE_UP_ANIMATION_DURATION
                            delay:0.3
           usingSpringWithDamping:SCALE_UP_SPRING_DAMPING
            initialSpringVelocity:SCALE_UP_SPRING_VELOCITY
                          options:0
                       animations:^{
                           cell.transform = transform;
                       }
                       completion:^(BOOL finished) {
                       }];
  }
  </code></pre>
  
  <hr>
  
  <p>EDIT: I basically want to replace highlighting in my cells with this scaling behaviour, it serves the exact same purpose and I want it to happen in exactly the same situation that the cell would be highlighted, so it seemed like an appropriate place to apply my transformation. </p>
  
  <p>Regardless, I had first tried overriding the  UIResponder touch methods in the cell subclass, but was observing the same behaviour. The sudden scale up happens even if I delete the scale up method so that it is never called, so my scale down is not being cancelled by the scale up animation. I can see through log statements that my scale down is called once, and the animation completion block is getting called with finsished == YES. The cell is getting scaled back up BEFORE the completion block is called (I have set the animation duration to be extra long to help in debugging). This seems to happen when I touch on the cell and then quickly scroll, so I guess the scrolling has something to do with it.</p>