title: UITapGestureRecognizer selector not being invoked
body: <p>Inside of my main window's root view controller class, I have set a UITapGestureRecognizer property. I've added this property to an image property through the addGestureRecognizer method during the call to the overridden viewDidLoad function. I have also set image.isUserInteractionEnabled to true. </p>
  
  <pre><code>override func viewDidLoad() {
     image.addGestureRecognizer(tap)
     image.isUserInteractionEnabled = true
  
     self.view.addSubview(image)
  }
  
  var tap = UITapGestureRecognizer(target: self, action: #selector(imagePressed(_ :)))
  </code></pre>
  
  <p>Sadly, this does not result in imagePressed() being called when run. What's confusing me is the fact that the following code produces the intended result.</p>
  
  <pre><code>override func viewDidLoad() {
     var tap = UITapGestureRecognizer(target: self, action:#selector(imagePressed(_ :)))
     image.addGestureRecognizer(tap)
     image.isUserInteractionEnabled = true
  
     self.view.addSubview(image)
  }
  </code></pre>
  
  <p>So my question is, why does the UITapGestureRecognizer's selector not get invoked during the first case?</p>
  
  <p>Using Swift 3 and Xcode 8.2.1</p>