title: How to implement UIVisualEffectView in UITableView with adaptive segues
body: <p>I would like to implement <code>UIVisualEffectView</code> to apply a blur effect to a view to show the view that lies behind it. </p>
  
  <p>This view that should have its background blurred is a <code>UITableViewController</code> that is embedded in a <code>UINavigationController</code>, and it will either be presented in a popover on iPad or it will be presented full screen modally on iPhone, thanks to iOS 8 adaptive segues (Present as Popover). When this view controller is in a popover I want the background to blur what's underneath the popover, and when it's presented full screen I want the background to blur the previous view controller. </p>
  
  <p>I have tried to implement this and have not been successful. I cannot even get the blur effect to work for the popover. I thought this code should do the trick:</p>
  
  <pre><code>//In viewDidLoad on the UITableViewController subclass:
  let effectView = UIVisualEffectView(effect: UIBlurEffect(style: .Light))
  effectView.frame = tableView.frame
  tableView.addSubview(effectView)
  </code></pre>
  
  <p>I also tried adding the subview to the <code>tableView.backgroundView</code>, I tried setting the <code>backgroundView</code> to my <code>effectView</code>, I tried using Autolayout constraints instead of setting the frame, but nothing has worked. Can you help me accomplish the desired behavior?</p>
  
  <p>An example of what I am trying to obtain:<br>
  iPad popover:<br>
  <img src="https://i.stack.imgur.com/ZS4Sx.jpg" alt="enter image description here"></p>
  
  <p>iPhone modal presentation:<br>
  <img src="https://i.stack.imgur.com/ryhjA.png" alt="enter image description here"></p>