使 Swift 中的计时器无效

Question

I am attempting to create an app in Xcode. I have a screen that switches the label every 30 seconds and that after x number of minutes, will switch to a screen that says Done!. There is also a return button to the original view. Currently, it freezes after completing x minutes and doesn't switch to the Done! screen. Additionally, if I return to the main view and then attempt to generate exercises again, the timer will count down by 2 seconds instead of 1.

Here is my code. Any tips would be appreciated!

import UIKit

var overallTime = minutes * 60
var timeLeft = 30
let resetTime = 30
var newE = true
var over = false

class ExerciseViewController: UIViewController {


    @IBOutlet weak var time: UILabel!
    @IBOutlet weak var progress: UIProgressView!
    @IBOutlet weak var currExercise: UILabel!

    let exercises = ["crunches", "bicycles", "leg lifts", "left crunches", "right crunches", "left cross crunches", "right cross crunches", "plank",
    "penguins", "wipers", "scissors", "flutter kicks", "right leg climbs", "left leg climbs", "sit ups", "dead bugs", "russian twists", "toe touches",
    "leg lifts with butt bump", "left plank", "right plank", "back plank", "alternating side sit-ups", "butterfly sit ups", "c-curve"]

    var num = 0

    var total = minutes * 2

    var timer: Timer?

    var bigtimer: Timer?

    override func viewDidLoad() {
        super.viewDidLoad()
        resetView()
        // Do any additional setup after loading the view.
        pickExercise()
        self.createTimer()
    }

    func pickExercise() {
        let index = Int.random(in: 0 ..< exercises.count)
        let curr = exercises[index]
        currExercise.text = String(curr)
        updateProgress()
        num += 1
    }

    func updateProgress() {
        let change: Float = Float(num) / Float(total)
        self.progress.progress = change
    }

    func resetView() {
        timer?.invalidate()
        bigtimer?.invalidate()
        timer = nil
        bigtimer = nil
        total = minutes * 2
        num = 0
        timeLeft = resetTime
        overallTime = minutes * 60
    }
}

extension ExerciseViewController {

    @objc func updateTimer() {
        if timeLeft <= 0 {
            timeLeft = resetTime
            time.textColor = UIColor.black
            pickExercise()
            if num > total {
                time.text = ""
            }
            else {
                time.text = String(timeLeft)
            }
        }
        else {
            timeLeft -= 1
            if timeLeft <= 10 {
                time.textColor = UIColor.red
            }
            if num > total {
                time.text = ""
            }
            else {
                time.text = String(timeLeft)
            }
        }

    }

    @objc func updateBigTimer() {
        if overallTime <= 0 {
            resetView()
            performSegue(withIdentifier: "Completed" , sender: self)
        }
        else {
            overallTime -= 1
        }
    }

    func createTimer() {
      // 1
      if timer == nil {
        // 2
        timer = Timer.scheduledTimer(timeInterval: 1.0,
                                     target: self,
                                     selector: #selector(updateTimer),
                                     userInfo: nil,
                                    repeats: true)
      }
        if bigtimer == nil {
            bigtimer = Timer.scheduledTimer(timeInterval: 1.0, target: self,
             selector: #selector(updateBigTimer),
             userInfo: nil,
            repeats: true)
        }
    }
}

Answer 1

is the below "timer = Timer..." intentional? or by mistake and it should be "bigtimer = Timer..." ?

if bigtimer == nil {
        timer = Timer.scheduledTimer(timeInterval: 1.0, target: self,
         selector: #selector(updateBigTimer),
         userInfo: nil,
        repeats: true)
    }

because initializing "timer" the second time, it will remove the reference of the first one, but it will keep the first timer running with no reference.