Timer in Apps (Swfit 3, Xcode 8, iOS)

In this example I start a timer as soon as I enter the second view controller after clicking the "START MY RANDOM WORKOUT" button. Here is the code for that second view:

 
import UIKit

class ExerciseVc: UIViewController {

    @IBOutlet weak var timerLabel: UILabel!
    
    @IBOutlet weak var icon: UIImageView!
    var timer: Timer!
    var timeLeft = 60
    
    override func viewDidLoad() {
        super.viewDidLoad()

        // Call setTimeLeft every 1 second
        timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: 
            #selector(self.setTimeLeft), userInfo: nil, repeats: true)
        icon.image = #imageLiteral(resourceName: "situp")
    }

    func setTimeLeft() {
        timeLeft -= 1 // Subtract one second
        
        if timeLeft == 0 {
            stop()
        }
        
        timerLabel.alpha = 1
        timerLabel.transform = CGAffineTransform(scaleX: 1.4, y: 1.4)
        
        UIView.animate(withDuration: 1, animations: {
            self.timerLabel.text = "\(self.timeLeft)"
            self.timerLabel.alpha = 0.3
            self.timerLabel.transform = .identity
        })
    }
    
    @IBAction func stop(_ sender: UIButton) {
        stop()
    }
    
    // Show a white status bar instead of the default black one
    override var preferredStatusBarStyle: UIStatusBarStyle {
        get {
            return UIStatusBarStyle.lightContent
        }
    }
    
    func stop() {
        timer.invalidate() // Stop the timer
        dismiss(animated: true, completion: nil)
    }
}
 

(Swift 3)