title: How to animate a NSLayoutConstraint within a CAAnimationGroup
body: <p>I had for example this in pre-autolayout times which was added to a CAAnimationGroup.</p>
  
  <pre><code>CABasicAnimation *resizeAnimation = [CABasicAnimation animationWithKeyPath:@"bounds.size"];
  [resizeAnimation setToValue:[NSValue valueWithCGSize:CGSizeMake(10.0f, 10.0f)]];
  resizeAnimation.fillMode = kCAFillModeForwards;
  resizeAnimation.removedOnCompletion = NO;
  </code></pre>
  
  <p>Under autolayout I assume that now I will need to change the Constant property of my Constraints on the object.</p>
  
  <p>So could you please help me to understand how to prepare the animation of a constraint.</p>
  
  <p><strong>EDIT</strong> In Best Practices Mastering Auto Layout - at around 30m he does this on OSX with NSAnimationContext - he does not talk about iOS.</p>