Animate text change in UILabel (Label Fade Animation)

extension_FadeTransitionView.swift

// Usage: insert view.fadeTransition right before changing content
extension UIView {
    func fadeTransition(_ duration:CFTimeInterval) {
        let animation = CATransition()
        animation.timingFunction = CAMediaTimingFunction(name:
            kCAMediaTimingFunctionEaseInEaseOut)
        animation.type = kCATransitionFade
        animation.duration = duration
        layer.add(animation, forKey: kCATransitionFade)
    }
}

ViewController.swift

class ViewController: UIViewController {

    @IBOutlet weak var label: UILabel!
    var count = 0

    @IBAction func doAction(_ sender: UIButton) {
        // This will fade:
        label.fadeTransition(0.4)
        count += 1
        label.text = "\(count)"
    }
}

swift 5.0 code

extension UIView {
func fadeTransition(_ duration:CFTimeInterval) {
let animation = CATransition()
animation.timingFunction = CAMediaTimingFunction(name:
CAMediaTimingFunctionName.easeInEaseOut)
animation.type = CATransitionType.fade
animation.duration = duration
layer.add(animation, forKey: CATransitionType.fade.rawValue)
}
}