Dispatching events to later in Swift.

After.swift

func After(after: NSTimeInterval, op: () -> ()) {
    After(after, op, nil)
}

func After(after: NSTimeInterval, op: () -> (), completion: (() -> Void)?) {
    let seconds = Int64(after * Double(NSEC_PER_SEC))
    var dispatchTime = dispatch_time(DISPATCH_TIME_NOW, seconds)
    dispatch_after(dispatchTime, dispatch_get_main_queue()) {
        let blockOp = NSBlockOperation(block: op)
        blockOp.completionBlock = completion
        NSOperationQueue.mainQueue().addOperation(blockOp)
    }
}