Simple MVC Timer- Swift

Question

I know this is a super basic question, I am trying to refactor my code atm and am running into trouble with the timer. All I am trying to do is just get a simple countdown timer to print to the console

Here is my code snippet right now

VC------

var seconds = 60

override func viewDidLoad() {
    super.viewDidLoad()
    self.modelInstance.gameTimerMethod(timeParam: self.seconds)     
}

MODEL-----

func gameTimerMethod(timeParam : Int)  {
    gameTimer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(decreaseGameTimer(secondsParam:)), userInfo: timeParam, repeats: true)
    print (timeParam)
}

func decreaseGameTimer(secondsParam: Int) {
    var printNumber = secondsParam
    printNumber -= 1
    print (printNumber)
}

Ideally what I want this to do in the console is simply countdown from 60 for now at a rate of one number per second. Although the console is logging at a rate of one number per second, it is for some reason repeatedly logging the number 105553117734207, instead of a 60 seconds countdown.

Thanks!

Answer 1

The value passed to decreaseGameTimer is the Timer instance. It has a property userInfo that has a reference to the object passed to the Timer constructor.

Create a class to hold your count, and then pass an instance of that class to the timer's userInfo:

class Model {

    class TimerInfo {
        var count: Int

        // Pointer to function or closure to call when value changes
        var callback: ((Int) -> Void)?

        init(start: Int, callback: @escaping (Int) -> Void) {
            count = start
            self.callback = callback
        }

        deinit {
            print("TimerInfo deinit")
        }
    }

    @objc func decreaseGameTimer(_ timer: Timer) {
        if let userInfo = timer.userInfo as? TimerInfo {
            userInfo.count -= 1

            // call callback with new value
            userInfo.callback?(userInfo.count)

            print(userInfo.count)
            if userInfo.count == 0 {
                print("done")
                timer.invalidate()
            }
        }
    }

    func gameTimerMethod(timeParam: Int, callback: @escaping (Int) -> Void) {
        _ = Timer.scheduledTimer(timeInterval: 1, target: self,
                                 selector: #selector(decreaseGameTimer),
                                 userInfo: TimerInfo(start: timeParam, callback: callback),
                                 repeats: true)
    }
}

Then you'd call it like this:

override func viewDidLoad() {
    super.viewDidLoad()

    // The closure that follows the gameTimerMethod call is using trailing
    // closure syntax.  It gets passed to gameTimerMethod as the second
    // parameter named callback.  This closure will get called every
    // second until the timer finishes.

    self.modelInstance.gameTimerMethod(timeParam: self.seconds) { value in
        self.label.text = "\(value)"
    } 

    // Just for fun, lets run a second one at the same time
    self.modelInstance.gameTimerMethod(timeParam: 10) { value in
        self.label2.text = "\(value)"
    }   
}