UIView.animateWithDuration swift loop animation
No need to do the completion block approach, just use the animation options argument:
updated for Swift 3.0
UIView.animate(withDuration: 2.0, delay: 0, options: [.repeat, .autoreverse], animations: { coloredSquare.frame = CGRect(x: 120, y: 220, width: 100, height: 100)}, completion: nil)If for any reason you want to stop the animation later, just use:
coloredSquare.layer.removeAllAnimations()
UIView.animate(withDuration: 3.0, delay: 0.0, options: [.curveLinear, .repeat], animations: { () -> Void in coloredSquare.frame = CGRect(x: 120, y: 220, width: 100, height: 100)}, completion: { (finished: Bool) -> Void in})