DispatchSourceTimer和Swift 3.0 [英] DispatchSourceTimer and Swift 3.0

问题描述

我不知道如何在Swift 3.0中使调度计时器重复工作.我的代码:

I can't figure out how to make dispatch timer work repeatedly in Swift 3.0. My code:

let queue = DispatchQueue(label: "com.firm.app.timer",
                          attributes: DispatchQueue.Attributes.concurrent)
let timer = DispatchSource.makeTimerSource(flags: DispatchSource.TimerFlags(rawValue: UInt(0)),
                                           queue: queue)

timer.scheduleRepeating(deadline: DispatchTime.now(),
                        interval: .seconds(5),
                        leeway: .seconds(1)
)

timer.setEventHandler(handler: {
     //a bunch of code here
})

timer.resume()

计时器仅触发一次，不会像应有的那样重复自身.我该如何解决?

Timer just fires one time and doesn't repeat itself like it should be. How can I fix this?

推荐答案

确保计时器不会超出范围.与Timer不同(在其上安排RunLoop会保留强引用，直到Timer无效)，您需要维护自己对GCD计时器的强引用，例如:

Make sure the timer doesn't fall out of scope. Unlike Timer (where the RunLoop on which you schedule it keeps the strong reference until the Timer is invalidated), you need to maintain your own strong reference to your GCD timers, e.g.:

var timer: DispatchSourceTimer?

private func startTimer() {
    let queue = DispatchQueue(label: "com.firm.app.timer", attributes: .concurrent)

    timer?.cancel()        // cancel previous timer if any

    timer = DispatchSource.makeTimerSource(queue: queue)

    timer?.schedule(deadline: .now(), repeating: .seconds(5), leeway: .milliseconds(100))

    // or, in Swift 3:
    //
    // timer?.scheduleRepeating(deadline: .now(), interval: .seconds(5), leeway: .seconds(1))

    timer?.setEventHandler { [weak self] in // `[weak self]` only needed if you reference `self` in this closure and you want to prevent strong reference cycle
        print(Date())
    }

    timer?.resume()
}

private func stopTimer() {
    timer?.cancel()
    timer = nil
}

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