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timerswift3
Hope
Hope

Reputation: 2326

Using Swift 3 Stopping a scheduledTimer, Timer continue firing even if timer is nil

We call startTimer function to start a timer. When we wanted to stop it we call stopTimerTest function but after we called stopTimer function the timerTestAction keeps firing. To check the timer condition we used print and print in timerActionTest returns nil.

var timerTest: Timer? = nil

func startTimer () {
    timerTest =  Timer.scheduledTimer(
        timeInterval: TimeInterval(0.3),
        target      : self,
        selector    : #selector(ViewController.timerActionTest),
        userInfo    : nil,
        repeats     : true)
}

func timerActionTest() {
    print(" timer condition \(timerTest)")
}

func stopTimerTest() {
    timerTest.invalidate()
    timerTest = nil
}

Upvotes: 52

Views: 87229

Answers (5)

Deepu George Jacob
Deepu George Jacob

Reputation: 474

Full working code

import UIKit


class ViewController: UIViewController {


var timer:Timer? = nil
var countValue = 60;


@IBAction func buttonClicked(_ sender: UIButton) {
    
    self.timer?.invalidate()
    self.timer = nil
    self.timer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(countDown), userInfo: nil, repeats: true)
}

@objc
func countDown() {
    if countValue>1 {
        countValue -= 1
    } else {
        self.timer?.invalidate()
        self.timer = nil
    }
    print("\(countValue) Seconds")
}}

Upvotes: 0

Sandeep Maurya
Sandeep Maurya

Reputation: 2099

Make sure when you call StartTimer it is nil and if you call StartTimer twice without calling StopTimer. You will lose your original pointer and you can't stop it.

 var timer : Timer? = nil {
        willSet {
            timer?.invalidate()
        }
    }

Start and Stop timer like ...

func startTimer() {
    stopTimer()
    guard self.timer == nil else { return }
    self.timer = Timer.scheduledTimer(timeInterval: 10, target: self, selector: #selector(self.fetchData), userInfo: nil, repeats: true)
}

func stopTimer() {
    guard timer != nil else { return }
    timer?.invalidate()
    timer = nil
}

Upvotes: 12

Mat
Mat

Reputation: 6324

Try to make the following changes to your code:

First, you have to change the way you declare timerTest

var timerTest : Timer?

then in startTimer before instantiating check if timerTest is nil 

func startTimer () {
  guard timerTest == nil else { return }

  timerTest =  Timer.scheduledTimer(
      timeInterval: TimeInterval(0.3),
      target      : self,
      selector    : #selector(ViewController.timerActionTest),
      userInfo    : nil,
      repeats     : true)
}

Finally in your stopTimerTest you invalidate timerTest if it isn't nil 

func stopTimerTest() {
  timerTest?.invalidate()
  timerTest = nil
}

Upvotes: 127

Rob Napier
Rob Napier

Reputation: 299355

Most likely you've called startTimer twice without calling stopTimerTest. If you do that, you'll lose your pointer to the original timer and never be able to invalidate it.

The typical approach is to manage invalidation as a part of setting:

var timerTest : Timer? = nil {
    willSet {
        timerTest?.invalidate()
    }
}

Then stopping is just setting to nil:

func stopTimerTest() {
    timerTest = nil
}

Upvotes: 45

Igor
Igor

Reputation: 12303

Check, are you really call stopTimerTest(), because timerTest.invalidate() is correct for stopping timer.

func stopTimerTest() {
    print("stopTimer")
    timerTest.invalidate()
}

Upvotes: 5

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