title: Change UIWindow backgroundColor from UIViewController?
body: <p>I have a UIViewController embedded in a UINavigationController. Inside my UIViewController I want to change the background color of the main UIWindow: </p>
  
  <pre><code>let appDelegate  = UIApplication.sharedApplication().delegate as! AppDelegate
  appDelegate.window!.backgroundColor = UIColor.blueColor()
  </code></pre>
  
  <p>The previous code work fine on iOS8 but in iOS7 there is no change in the background color of the UIWindow when it is embedded in a UINavigationController.</p>
  
  <p><strong>How can I change the background color of the UIWindow inside my UIViewController in iOS7?</strong></p>