Using an NSTimer in Swift

问题:

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

class AppDelegate: NSObject, NSApplicationDelegate {

    var myTimer: NSTimer? = nil

    func timerFunc() {
        println("timerFunc()")
    }

    func applicationDidFinishLaunching(aNotification: NSNotification?) {
        myTimer = NSTimer(timeInterval: 5.0, target: self, selector:"timerFunc", userInfo: nil, repeats: true)
    }
}

回答1:

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

NSTimer.scheduledTimerWithTimeInterval(0.5, target: self, 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:

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

回答2:

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'

回答3:

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

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

回答4:

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!) {
    ...
}

回答5:

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)

回答6:

Swift 3.0 syntax for the run loop thingy:

RunLoop.current.add(myTimer, forMode: .commonModes)

回答7:

This is a bit of code, that demonstrates how to call a function (delayed) with AND without a parameter.

Use this in a new project in xCode (singleViewApplication) and put the code into the standard viewController:

class ViewController: UIViewController {

    override func viewDidLoad() {

        super.viewDidLoad()

        NSTimer.scheduledTimerWithTimeInterval(2.0, target: self, selector: Selector("delayedFunctionWithoutParameter:"), userInfo: nil, repeats: false)

        let myParameter = "ParameterStringOrAnyOtherObject"

        NSTimer.scheduledTimerWithTimeInterval(4.0, target: self, selector: Selector("delayedFunctionWithParameter:"), userInfo: myParameter, repeats: false)
    }

    // SIMPLE TIMER - Delayed Function Call
    func delayedFunctionWithoutParameter(timer : NSTimer) {
        print("This is a simple function beeing called without a parameter passed")
        timer.invalidate()
    }

    // ADVANCED TIMER - Delayed Function Call with a Parameter
    func delayedFunctionWithParameter(timer : NSTimer) {

        // check, wether a valid Object did come over
        if let myUserInfo: AnyObject = timer.userInfo {
            // alternatively, assuming it is a String for sure coming over
            // if let myUserInfo: String = timer.userInfo as? String {
            // assuming it is a string comming over
            print("This is an advanced function beeing called with a parameter (in this case: \(myUserInfo)) passed")
        }

        timer.invalidate()
    }
}

Notice, that in any case you should implement the delayed function with the parameter (timer : NSTimer) to be able to invalidate (terminate, end) the timer. And with the passend "timer" you have also access to the userInfo (and there you can put any Object, not only String-Objects, as well collection types such as arrays and dictionaries).

Original Apples documentations says "" -> The timer passes itself as the argument, thus the method would adopt the following pattern: - (void)timerFireMethod:(NSTimer *)timer Read fully -> here

回答8:

Since this thread made me try to put the timer on a RunLoop myself (which solved my problem), I post my specific case as well - who knows maybe it helps somebody. My timer is created during app start up and initialisation of all the objects. My problem was that, while it did schedule the timer, it still never fired. My guess is, this was the case because scheduledTimerWithTimeInterval was putting the timer on a different RunLoop during startup of the App. If I just initialise the timer and then use NSRunLoop.mainRunLoop().addTimer(myTimer, forMode:NSDefaultRunLoopMode) instead, it works fine.

回答9:

With swift3, you can run it with,

var timer: Timer?
func startTimer() {

    if timer == nil {
        timer = Timer.scheduledTimer(timeInterval: 3, target: self, selector: #selector(self.loop), userInfo: nil, repeats: true)
    }
}

func stopTimer() {
    if timer != nil {
        timer?.invalidate()
        timer = nil
    }
}

func loop() {
    //do something
}

回答10:

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) { }