UILabel text animation

gistfile1.txt

let label = UILabel()
label.frame = CGRect(x: 0.0, y: 0.0, width: 400.0, height: 75.0)
label.backgroundColor = UIColor.whiteColor()
label.font = UIFont.preferredFontForTextStyle(UIFontTextStyleTitle1)
label.textAlignment = .Center
label.text = "Hello, world!"

let fadeTransition = CATransition()
fadeTransition.duration = 0.2

CATransaction.begin()
CATransaction.setCompletionBlock({
    label.text = "Goodnight, moon..."
    label.layer.addAnimation(fadeTransition, forKey: kCATransition)
})

label.text = ""
label.layer.addAnimation(fadeTransition, forKey: kCATransition)

CATransaction.commit()