title: Swift Infinite Fade in and Out Loop
body: <p>How can I make a effect in swift similar to this:
  <a href="https://i.stack.imgur.com/tywWN.gif" rel="noreferrer"><img src="https://i.stack.imgur.com/tywWN.gif" alt="enter image description here"></a></p>
  
  <p>I want the animation to loop forever.  </p>