title: Swift: transparent background for UIViewAlertController
body: <p>there are many answers on Stack Overflow about this but none seem to work. how do you make the background color of a UIAlertViewController truly clear?</p>
  
  <p>i have at the moment:</p>
  
  <pre><code>let errorAlert = UIAlertController(title: "Title", message: "Message", preferredStyle: UIAlertControllerStyle.Alert)
  let subview = errorAlert.view.subviews.first! as UIView
  let alertContentView = subview.subviews.first! as UIView
  alertContentView.backgroundColor = UIColor.clearColor()
  errorAlert.view.backgroundColor = UIColor.clearColor()
  showViewController(errorAlert, sender: self)
  </code></pre>
  
  <p>but the result is a kind of white tinted, transparent-ish background over the image... <strong>is there anyway to remove this tinted background?</strong></p>
  
  <p><a href="https://i.stack.imgur.com/Asgf2.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Asgf2.png" alt="enter image description here"></a></p>