title: UIViewController that implements protocol as an argument in Swift
body: <p>in my application I want to write function that takes as an parameter UIViewController that implements some protocol. In objective-c I could accomplish this by writing:</p>
  
  <pre><code>-(void)someFunction:(UIViewContoller&lt;MyProtocol&gt; *controller);
  </code></pre>
  
  <p>How can I create similar function in Swift?</p>