title: Pausing a UIView's key frame animations
body: <p>I'm currently creating a loading bar that I would like to pause and reverse if a specific action is taken. </p>
  
  <p>I have the following code below that animates one view in another. How would I go about pausing this animation and applying another animation on the CURRENT frame at that point in time for the animated object. I would like to be able to animate this bar down to the 0 width mark at any given time within the current animation. </p>
  
  <pre><code>-(void)animateProgressBar
  {
      CGRect endingFrame = self.frame;
  
      [UIView animateKeyframesWithDuration:self.time delay:0.0 options:0 animations:^{
          [UIView addKeyframeWithRelativeStartTime:0.0 relativeDuration:1.0 animations:^{
              self.loadingBar.frame = endingFrame;
          }];
      } completion:^(BOOL finished) {
          NSLog(@"TADA");
      }];
  }
  </code></pre>