Swift 4：如何在 UIbutton .settitle 中添加倒数计时器？

Question

I am trying to add a Countdown timer inside of my UIButton in the .settitle. How can I do this? The image below is what I am trying to accomplish.

Then once the timer gets to 0, I want the background color to change to a different color.

Here is the code I have so far.

let sendSMSAgainNumberOfTime: UIButton = {
    let button = UIButton(type: .system)
    button.backgroundColor = .black
    button.layer.cornerRadius = 7
    button.setTitle("SEND SMS AGAIN IN 36", for: .normal)
    button.setTitleColor(.white, for: .normal)
    button.titleLabel?.font = UIFont(name: "open sans", size: 16)
    return button
}()

Answer 1

You can try a timer

 var countTimer:Timer!

 var counter = 36

//

in viewDidLoad set it

 self.countTimer = Timer.scheduledTimer(timeInterval: 1 ,
                                              target: self,
                                              selector: #selector(self.changeTitle),
                                              userInfo: nil,
                                              repeats: true)

func changeTitle()
{
     if counter != 0
     {
         button.setTitle("SEND SMS AGAIN IN \(counter)", for: .normal)
         counter -= 1
     }
     else
     {
          countTimer.invalidate()

          button.backgroundColor = // set any color
     }

}

//

OR use IOS 10+ timer block

//

let sendSMSAgainNumberOfTime: UIButton = {
    let button = UIButton(type: .system)
    button.backgroundColor = .black
    button.layer.cornerRadius = 7
    button.setTitle("SEND SMS AGAIN IN 36", for: .normal)
    button.setTitleColor(.white, for: .normal)
    button.titleLabel?.font = UIFont(name: "open sans", size: 16)

    // timer block exists from ios 10 +

    if #available(iOS 10.0, *) {

        Timer.scheduledTimer(withTimeInterval: 1, repeats: true, block: { (t) in

            if(button.tag != 37)
            {
                button.setTitle("SEND SMS AGAIN IN \(36-button.tag)", for: .normal)

                button.tag += 1
            }
            else
            {
                t.invalidate()

                button.backgroundColor = // set any color
            }


        })
    } else {
        // Fallback on earlier versions
    }

    return button
}()

Answer 2

You can also do the following in Swift 5. This is a very simple countdown that prints each second remaining after button is tapped. Let me know if you have any questions (:

class ViewController: UIViewController {

    var secondsRemaining = 30

    @IBAction func startTimer(_ sender: UIButton) {

        Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { (Timer) in
            if self.secondsRemaining > 0 {
                print ("\(self.secondsRemaining) seconds")
                self.secondsRemaining -= 1
            } else {
                self.invalidate()
            }
        }

    }