poll.swift

func poll() {
    
    let backgroundQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)
    let source = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, backgroundQueue)
    
    let interval: UInt64 = UInt64(10) * NSEC_PER_SEC
    let leeway: UInt64 = UInt64(0.1) * NSEC_PER_SEC
    dispatch_source_set_timer(source, DISPATCH_TIME_NOW, interval, leeway)
    dispatch_source_set_event_handler(source) { () -> Void in
        self.pollDidFinish(source: source)
    }
    
    dispatch_resume(source)
}