Comment puis-je faire un compte à rebours avec NSTimer?

dans Swift 3.0, cela fonctionnera:

var counter = 30

override func viewDidLoad() {
    super.viewDidLoad()

    var _ = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(updateCounter), userInfo: nil, repeats: true)
}



func updateCounter() {
    //you code, this is an example
    if counter > 0 {
        print("\(counter) seconds to the end of the world")
        counter -= 1
}

Variable pour votre minuterie

var timer = 60

NSTimer avec 1,0 comme intervalle

var clock = NSTimer.scheduledTimerWithTimeInterval(1.0, target: self, selector: "countdown", userInfo: nil, repeats: true)

Ici vous pouvez diminuer la minuterie

func countdown() {
    timer--
}

Swift 3

private let NUMBER_COUNT_DOWN   = 3

var countDownLabel = UILabel()
var countDown = NUMBER_COUNT_DOWN
var timer:Timer?


private func countDown(time: Double)
{
    countDownLabel.frame = CGRect(x: 0, y: 0, width: 300, height: 300)
    countDownLabel.font = UIFont.systemFont(ofSize: 300)
    countDownLabel.textColor = .black
    countDownLabel.center = CGPoint(x: self.view.frame.width / 2, y: self.view.frame.height / 2)

    countDownLabel.textAlignment = .center
    self.view.addSubview(countDownLabel)
    view.bringSubview(toFront: countDownLabel)

    timer = Timer.scheduledTimer(timeInterval: time, target: self, selector: #selector(updateCountDown), userInfo: nil, repeats: true)
}

func updateCountDown() {
    if(countDown > 0) {
        countDownLabel.text = String(countDown)
        countDown = countDown - 1
    } else {
        removeCountDownLable()
    }
}

private func removeCountDownLable() {
    countDown = NUMBER_COUNT_DOWN
    countDownLabel.text = ""
    countDownLabel.removeFromSuperview()

    timer?.invalidate()
    timer = nil
}

Rendre compte à Rebours application Xcode 8.1, Swift 3

import UIKit
import Foundation

class ViewController: UIViewController, UITextFieldDelegate {

    var timerCount = 0
    var timerRunning = false

    @IBOutlet weak var timerLabel: UILabel! //ADD Label
    @IBOutlet weak var textField: UITextField! //Add TextField /Enter any number to Countdown

    override func viewDidLoad() {
        super.viewDidLoad()

        //Reset
        timerLabel.text = ""
        if timerCount == 0 {
            timerRunning = false
        }
}

       //Figure out Count method
    func Counting() {
        if timerCount > 0 {
        timerLabel.text = "\(timerCount)"
            timerCount -= 1
        } else {
            timerLabel.text = "GO!"

        }

    }

    //ADD Action Button
    @IBAction func startButton(sender: UIButton) {

        //Figure out timer
        if timerRunning == false {
         _ = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(ViewController.Counting), userInfo: nil, repeats: true)
            timerRunning = true
        }

        //unwrap textField and Display result
        if let countebleNumber = Int(textField.text!) {
            timerCount = countebleNumber
            textField.text = "" //Clean Up TextField
        } else {
            timerCount = 3 //Defoult Number to Countdown if TextField is nil
            textField.text = "" //Clean Up TextField
        }

    }

    //Dismiss keyboard
    func keyboardDismiss() {
        textField.resignFirstResponder()
    }

    //ADD Gesture Recignizer to Dismiss keyboard then view tapped
    @IBAction func viewTapped(_ sender: AnyObject) {
        keyboardDismiss()
    }

    //Dismiss keyboard using Return Key (Done) Button
    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        keyboardDismiss()

        return true
    }

}

https://github.com/nikae/CountDown-

Swift 4

Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(self.updateTime), userInfo: nil, repeats: true)

mise à Jour de la fonction

@objc func updateTime(){
    debugPrint("jalan")
}

Swift 4.1. La méthode updatetime sera appelée après chaque seconde et les secondes s'afficheront sur UIlabel.

     var timer: Timer?
     var totalTime = 60

     private func startOtpTimer() {
            self.totalTime = 60
            self.timer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(updateTimer), userInfo: nil, repeats: true)
        }

    @objc func updateTimer() {
            print(self.totalTime)
            self.lblTimer.text = self.timeFormatted(self.totalTime) // will show timer
            if totalTime != 0 {
                totalTime -= 1 . // decrease counter timer
            } else {
                if let timer = self.timer { 
                    timer.invalidate()
                    self.timer = nil
                }
            }
        }
    func timeFormatted(_ totalSeconds: Int) -> String {
        let seconds: Int = totalSeconds % 60
        let minutes: Int = (totalSeconds / 60) % 60
        return String(format: "%02d:%02d", minutes, seconds)
    }