title: show alertController from a custom class
body: <p>I'm trying to show an AlertController from a class that I've made.
  Since AlertController is a subclass of UIResponder I'm using the following line of code that Xcode is suggesting me</p>
  
  <pre><code>superclass?.presentViewController(alertController, animated: true, completion: nil)
  </code></pre>
  
  <p>But I cannot compile because AnyClass? does not have any member presentViewController.
  My class is a subclass of NSObject.</p>
  
  <p>Any other solution?
  Thanks</p>