title: How to properly dismiss modal viewcontroller with completion handler
body: <p>I have <code>viewController1</code> and <code>viewController2</code> which is modaly presented and I want to use the completion handler when I dismiss the 2nd, but I can't get the implementation. I thought that I have to write a function and just put it there like:</p>
  
  <pre><code>viewController.dismissViewControllerAnimated(true, completion: funcToCall())
  </code></pre>
  
  <p>but then I get this error: </p>
  
  <blockquote>
    <p>Cannot convert value of type '()' to expected argument type '(() ->
    Void)?'</p>
  </blockquote>
  
  <p>Anyone can explain me, how can I execute properly the completion handler, please?</p>