title: How do I animate a NSLayoutConstraint in Swift?
body: <p>I would like to animate an UIImageView. I declared a <code>NSLayoutConstraint</code> in <code>viewDidLoad</code> and used this code:</p>
  
  <pre><code>UIView.animate(withDuration: 1) {
      myConstraint.constant = 100
      self.view.layoutIfNeeded()
  }
  </code></pre>
  
  <p>Why doesn't my image move?</p>