title: How can I animate any UIView inside UITableViewCell?
body: <pre><code>let label = UILabel(frame: CGRectMake(20.0, 20.0, 15.0, 15.0))
  label.backgroundColor = UIColor.flamingoColor() 
  
  UIView.animateWithDuration(3.0, animations: {
      cell.addSubview(label)
      label.backgroundColor = UIColor.yellowColor()
  })
  </code></pre>
  
  <p>This code I put inside <code>tableView:cellForRowAtIndexPath:</code> -> result is a subview that has a yellow background, but I haven't seen any animation. The same is for method <code>tableView:didEndDisplayingCell:</code></p>
  
  <p>Which method should I use or what kind of animation should I put there to see any animations inside UITableViewCell. I know that I <strong>cannot</strong> animate existing labels, because these are with constraints.</p>