DispatchSourceTimer 和 Swift 3.0

Question

我不知道如何让调度计时器在 Swift 3.0 中重复工作。我的代码：

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()

定时器只会触发一次，不会像应有的那样重复。我该如何解决这个问题？

Answer 1

确保计时器不会超出范围。与Timer 不同（您安排它在RunLoop 上保留强引用直到Timer 无效），您需要维护自己对GCD 计时器的强引用，例如：

private var timer: DispatchSourceTimer?

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

    timer = DispatchSource.makeTimerSource(queue: queue)

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

    timer?.resume()
}

private func stopTimer() {
    timer = nil
}