Swift 自己写定时器

private var timer:
dispatch_source_t? =
nil

private func startTimer() {

let updateInterval:
UInt64 = 1

let interval = updateInterval *
NSEC_PER_SEC

let leeway:
UInt64 =
300000000 // UInt64(0.3) * interval

let queue =
dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,
0)

timer =
dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER,
0, 0, queue)

if timer !=
nil {

dispatch_source_set_timer(timer!,
dispatch_walltime(nil,
0), interval, leeway)

dispatch_source_set_event_handler(timer!, { () ->
Void
in

self.checkNewScreenshot()

})

}

dispatch_resume(timer!)

}



private func stopTimer() {

if timer !=
nil {

dispatch_suspend(timer!)

dispatch_resume(timer!)

timer =
nil

}

}