title: Create an UIAlertAction in Swift
body: <p>I would like to create the following <code>UIAlertAction</code>:</p>
  
  <p><img src="https://cdn-ak.f.st-hatena.com/images/fotolife/n/niwakk7/20141002/20141002183359.png" alt="img1"></p>
  
  <pre><code>@IBAction func buttonUpgrade(sender: AnyObject) {
  
             let alertController = UIAlertController(title: "Title",
          message: "Message",
          preferredStyle: UIAlertControllerStyle.Alert)
  
      let cancelAction = UIAlertAction(title: "Cancel", style: .Cancel) { (action) in
          // ...
      }
  
      alertController.addAction(cancelAction)
  }
  </code></pre>
  
  <p>I'm aware that an <code>UIAlertController</code> is initialized with a <code>title</code>, <code>message</code>, and whether it prefers to be displayed as an alert or action sheet.</p>
  
  <p>When the button is pressed I would like to display the alert, but <code>alert.show()</code> doesn't work. Why doesn't my code work?</p>