Using an NSTimer in Swift

Question

In this scenario, timerFunc() is never called. What am I missing?

class AppDelegate: NSObject, NSApplicationDelegate {

    var myTimer: NSTimer? = nil

             


        

Answer 1

i use a similar approach to Luke. Only a caveat for people who are "private methods" purists:

DO NOT make callback private in Swift.

If You write:

private func timerCallBack(timer: NSTimer){

..

you will get:

timerCallBack:]: unrecognized selector sent to instance... Terminating app due to uncaught exception 'NSInvalidArgumentException'

Answer 2

For Swift 3

var timer = Timer.scheduledTimer(timeInterval: 0.01, target: self, selector: #selector(ViewController.updateTimer), userInfo: nil, repeats: true);
RunLoop.current.add(timer, forMode: RunLoopMode.commonModes)

Answer 3

You can create a scheduled timer which automatically adds itself to the runloop and starts firing:

Swift 2

NSTimer.scheduledTimerWithTimeInterval(0.5, target: self, selector: "timerDidFire:", userInfo: userInfo, repeats: true)

Swift 3, 4, 5

Timer.scheduledTimer(withTimeInterval: 0.5, target: self, selector: #selector(timerDidFire(_:)), userInfo: userInfo, repeats: true)

Or, you can keep your current code, and add the timer to the runloop when you're ready for it:

Swift 2

let myTimer = NSTimer(timeInterval: 0.5, target: self, selector: "timerDidFire:", userInfo: nil, repeats: true)
NSRunLoop.currentRunLoop().addTimer(myTimer, forMode: NSRunLoopCommonModes)

Swift 3, 4, 5

let myTimer = Timer(timeInterval: 0.5, target: self, selector: #selector(timerDidFire(_:)), userInfo: nil, repeats: true)
RunLoop.current.add(myTimer, forMode: RunLoop.Mode.common)

Answer 4

NSTimer's are not scheduled automatically unless you use NSTimer.scheduledTimerWithTimeInterval:

myTimer = NSTimer.scheduledTimerWithTimeInterval(5.0, target: self, selector: "timerFunc", userInfo: nil, repeats: true)

Answer 5

As Drewag and Ryan pointed out, you need to create a scheduled timer (or schedule it yourself) It's easiest to create it scheduled already with:

myTimer = NSTimer.scheduledTimerWithTimeInterval(5.0, target: self, selector: "timerFunc:", userInfo: nil, repeats: true)

You also need to change your definition of timerFunc (and the associated selector) to take an argument and end with a ':'

func timerFunc(timer:NSTimer!) {
    ...
}

Answer 6

To do it with the method the OP suggests, you need to add it to a run loop:

myTimer = NSTimer(timeInterval: 5.0, target: self, selector:"timerFunc", userInfo: nil, repeats: true)
NSRunLoop.mainRunLoop().addTimer(myTimer, forMode:NSDefaultRunLoopMode)

The documentation also says that the target should take an argument, but it works without it.

func timerFireMethod(timer: NSTimer) { }