title: UIView center position during animation
body: <p>I would like to determine, what is the center position of a UIVIew (the middle point of the view) during an animation. An animation with UIViewPropertyAnimator like this:</p>
  <pre><code>let animator = UIViewPropertyAnimator(duration: 10, curve: .easeInOut)
   
  var circle : UIView!
  circle = UIView(frame: CGRect(x: 0.0, y: 0.0, width: 40.0, height: 40.0))
  circle.layer.cornerRadius = 20.0
  circle.backgroundColor = UIColor.blue
  self.view.addSubview(circle)
  
  animator.addAnimations {
      circle.center = CGPoint(x: 100,y: 100)
      //or any other point
  }
  animator.startAnimation()
  </code></pre>
  <p>If I print the circle.center property during the animation then I got just the destination position of the animation not the real position.</p>
  <pre><code>Timer.scheduledTimer(withTimeInterval: 0.2, repeats: true, block: {
  [weak self] (Timer) -&gt; Void in
  if let circleCenterPosition = self?.circle.center
  {
      print(circleCenterPosition)
  }
  })
  </code></pre>
  <p>After this print I saw this on the console:</p>
  <blockquote>
  <p>(100.0, 100.0)</p>
  <p>(100.0, 100.0)</p>
  <p>...</p>
  </blockquote>
  <p>How can I print the real position during the animation?</p>
  <p>Thanks.</p>