Check out example codes for "Blinking effect on UILabel". It will help you in understanding the concepts better.

Code Example 1

extension UILabel {

    func startBlink() {
        UIView.animate(withDuration: 0.8,
              delay:0.0,
              options:[.allowUserInteraction, .curveEaseInOut, .autoreverse, .repeat],
              animations: { self.alpha = 0 }, 
              completion: nil)
    }

    func stopBlink() {
        layer.removeAllAnimations()
        alpha = 1
    }
}

//Useage e.g. 
loginButton.blink(duration: 1, delay: 0.1, alpha: 0.0100000003)

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