Cancellable delayed task in Swift.

CancellableDelayedTask.swift

class CancellableDelayedTask {
    var cancelled = false
    func run(delay: Double, task: () -> Void ) {
        let time = dispatch_time(DISPATCH_TIME_NOW, Int64(delay))
        dispatch_after(time, dispatch_get_main_queue()) { [unowned self] () -> Void in
            if !self.cancelled {
                task()
            }
        }
    }
    func cancel() {
        cancelled = true
    }
}

example.swift

let task = CancellableDelayedTask()
task.run(3.0 * Double(NSEC_PER_SEC)) { () -> Void in
    // Do something...
}
task.cancel()