Swift test from original Nick Lockwood article: https://gist.github.com/nicklockwood/d374033b27c62662ac8d (animated UILabel on text changes)

AnimatedLabel

import UIKit

class ViewController: UIViewController {
    let magicLabel = AnimatedLabel(frame: CGRectMake(100, 100, 300, 20));

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        magicLabel.text = "Magic label"
        self.view.addSubview(magicLabel);
    }
    @IBAction func buttonPressed(sender: UIButton) {
        if let labelText = magicLabel.text? {
            magicLabel.text = newString(labelText)
        }

    }
    func newString(previousString: String) -> String {
        if previousString == "Magic label" {
            return "Aumagically animated"
        }
        return "Magic label"
    }
}
class AnimatedLabel: UILabel {
    override func actionForLayer(layer: CALayer!, forKey event: String!) -> CAAction! {
        if (event == "contents"){
            var transition = CATransition()
            transition.type = kCATransitionMoveIn
            transition.subtype = kCATransitionFromTop
            return transition
        }
        return super.actionForLayer(layer, forKey: event)
    }
}