title: What are these little square symbols in Swift 3 code?
body: <p>Sorry I have been away from programming for a while (since before Swift 3) and even back then I wasn't real good at it.  Anyway I was playing around with SwiftyCam:</p>
  
  <p><a href="https://github.com/Awalz/SwiftyCam" rel="nofollow noreferrer">https://github.com/Awalz/SwiftyCam</a></p>
  
  <p>And I notice these squares in the code.  Anyone know what these things are?  Never saw this before, and not sure if it's new with Swift 3 or if I just haven't come across them. Example:</p>
  
  <pre><code>func swiftyCam(_ swiftyCam: SwiftyCamViewController, didFocusAtPoint point: CGPoint) {
     let focusView = UIImageView(image: #imageLiteral(resourceName: "focus"))
     focusView.center = point
     focusView.alpha = 0.0
     view.addSubview(focusView)
  }
  </code></pre>
  
  <p>Okay well I can't even paste it.  It's before the word "focus" and there are no quotations it's just (resourceName: ***insert square here***focus)</p>
  
  <p>I hope this makes sense and sorry if it's a dumb question I just don't know how to look something like this up because you can't type squares int he docs or anything.</p>