A little trick I learnt today to change the text of a label with a crossfade...

let animation = CATransition()
animation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseOut)
animation.type = kCATransitionFade
animation.duration = 0.5
self.label.layer.addAnimation(animation, forKey: "kCATransitionFade")
self.label.text = "new copy"