title: Using CABasicAnimation to rotate a UIImageView more than once
body: <p>I am using a CABasicAnimation to rotate a <code>UIImageView</code> 90 degrees clockwise, but I need to have it rotate a further 90 degrees later on from its position after the initial 90 degree rotation.</p>
  
  <pre><code>CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];
  animation.duration = 10;
  animation.additive = YES;
  animation.removedOnCompletion = NO;
  animation.fillMode = kCAFillModeForwards;
  animation.fromValue = [NSNumber numberWithFloat:DEGREES_TO_RADIANS(0)];
  animation.toValue = [NSNumber numberWithFloat:DEGREES_TO_RADIANS(90)];
  [_myview.layer addAnimation:animation forKey:@"90rotation"];
  </code></pre>
  
  <p>Using the code above works initially, the image stays at a 90 degree angle. If I call this again to make it rotate a further 90 degrees the animation starts by jumping back to 0 and rotating 90 degrees, not 90 to 180 degrees.</p>
  
  <p>I was under the impression that <code>animation.additive = YES;</code> would cause further animations to use the current state as a starting point.</p>
  
  <p>Any ideas?</p>