Timer Function

There is simple example timer in swift 3.0

class ViewController: UIViewController {

    var Timer :Foundation.Timer = Foundation.Timer()

    override func viewDidLoad() {

        Timer = Foundation.Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(ViewController.UpdateTimer), userInfo: nil, repeats: true)

}

    func UpdateTimer(){

        //Do something up to you

}

    @IBAction func onClickedStopStart(_ sender: AnyObject) {

// Stop and resume timer

        if Timer.isValid {

            Timer.invalidate()

            btnStartStop.setTitle("Start", for: .normal)

        }else{

            Timer = Foundation.Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(ViewController.UpdateTimer), userInfo: nil, repeats: true)

            btnStartStop.setTitle("Stop", for: .normal)

        }

    }

}