title: Call a method every time animation repeats
body: <p>I need to call a certain method before my animation repeats.
  I don't know where to place that line of code.</p>
  
  <p>This is my code for animating an object:</p>
  
  <pre><code>[UIView animateWithDuration:speed
                        delay:delay
                      options:UIViewAnimationOptionAllowUserInteraction|UIViewAnimationOptionCurveLinear|UIViewAnimationOptionRepeat
                   animations:^(void){
  
                       cloud.frame = (CGRectMake(cloud.frame.origin.x, cloud.frame.origin.y+600, cloud.frame.size.width, cloud.frame.size.height));
  
                   }completion:^(BOOL finished){
                       if (finished){
                           [cloud setBackgroundImage:[UIImage imageNamed:@"cloudWhite.png"] forState:UIControlStateNormal];
                       }
                   }];
  </code></pre>
  
  <p>Method called in <strong><em>completion</em></strong> part will not be executed before every repeat but only after whole animation is complete, together with al repeats - which is, in this case - never.</p>
  
  <p>My question is, how to call a method before every animation repeat?</p>