swift3，my timer can't stop. why?

Question

this is i seting a timer function, the code like this:

@IBAction func start(_ sender: UIButton) {

    Timer.scheduledTimer(timeInterval: 1,
                         target: self,
                         selector:#selector(ViewController.action),
                         userInfo: nil,
                         repeats: true)
}

@objc func action() {

    hoursMinutesSeconds()
    if stop == true{
        start = false
        timer.invalidate()
        timer.invalidate()
        time = 0 
    }
}

@IBAction func stop(_ sender: UIButton){

    start = false
    timer.invalidate()
    timer.invalidate()
    time = 0           
}

but, when i click the stop func, this function not work. mean is the timer not stop. timer stil working…… why？ thank you for your time!!

Answer 1

I think you didn't set timer value

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

Answer 2

Ensure that you are invalidating correct instance of Timer. Like in start function , you didn't assign timer instance to any object, but in stop function ,you are using timer vaiable to stop that timer. Which means you try to invalidate a variable, which never instantiated.

Still try below function to stop timer, after assigning timer variable .

@IBAction func stop(_ sender: UIButton) {

       start = false
       timer.invalidate()
       timer = nil
       time = 0
    }

Hope this work

Answer 3

First you have to declare it as fileprivate as below:

fileprivate var timer = Timer()

@IBAction func start(_ sender: UIButton) {

        self.timer = Timer.scheduledTimer(timeInterval: 4,
                                                      target: self,
                                                      selector: #selector(self.updateTimerForLocation),
                                                      userInfo: nil,
                                                      repeats: true)

}

@IBAction func stop(_ sender: UIButton) {

   timer.invalidate()


}

Answer 4

you are confusing between variable stop and func stop.
also you dont need 2 parameter to manage stop/start status

-- for your question, you should retain the timer variable to able to use it in other func declare a global timer

var timer: Timer!

then

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

now you can invalidate it anywhere