Derreck Derreck - 2 months ago 227
Swift Question

DispatchSourceTimer and Swift 3.0

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()


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

Rob Rob
Answer

Make sure the timer doesn't fall out of scope. Unlike NSTimer, you need to maintain a 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 = DispatchSource.makeTimerSource(flags: [], queue: queue)

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

    timer?.setEventHandler {
        print(Date())
    }

    timer?.resume()
}

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