looking for a timer function I can use with using @objc

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Created Feb ’22

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I am migrating a c# app to Xcode swift and have been looking for a swift equivalent to c# Time.time which is the time in seconds since app became active. I have seen the Timer class but all examples I have seen depend on using #selector and @objc. How do I get the Timer class to use a completion function? Or Is there another way of getting the app run time in seconds?

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Answer 1

Systems Engineer OP

Apple

Feb ’22

How do I get the Timer class to use a completion function?

Are you looking for something like this:

let _ = Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { myTimer in
    print("My Timer Fired")
}

// Or something that ends after 5 seconds....

var repeats = 1

Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { timer in
    print("Timer \(repeats)")
    repeats += 1

    if repeats > 5 {
        timer.invalidate()
    }
}

Otherwise, yes, if you are using #selector you will need to use the @objc attribute because this interacts with the Objective-C runtime.

class TimerClass: NSObject {
    var repeats = 1
    var timer: Timer?
    
    func startTimer() {
        timer = Timer.scheduledTimer(timeInterval: 1.0,
                                     target: self,
                                     selector: #selector(objCTimerCallback),
                                     userInfo: nil,
                                     repeats: true)
    }
    
    @objc func objCTimerCallback() {
        print("Timer: \(repeats)")
        repeats += 1

        if repeats > 5 {
            timer?.invalidate()
        }
    }
}

let time = TimerClass()
time.startTimer()

Regarding:

Or Is there another way of getting the app run time in seconds?

There is no out-of-the-box API for this but you could look MetricKit if you need more information on app metrics and data.

Matt Eaton
DTS Engineering, CoreOS
meaton3@apple.com

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