title: Make an animation loop endlessly until I press a button in Swift iOS. How?
body: <p>Here's my code for the animation:   </p>
  
  <pre><code>UIView.animateWithDuration(3, 
    animations: {self.redBar.center = CGPointMake(self.redBar.center.x + 600, self.redBar.center.y + 600)},
    completion: nil)
  </code></pre>
  
  <p>I want to make it loop until I press a button. How?</p>