Swift alert 倒计时

let title: String = "您的开奖时间为"
let time: String = "2017-10-23 12:23:18"
let count_down: NSString = "6" as NSString
var countdown = count_down.integerValue
let timeout: String = "开奖时间已超时,请重新获取"
let alertVc = UIAlertController.init(title: nil, message: title + "\n" + time, preferredStyle: UIAlertControllerStyle.alert)
let alertAction0 = UIAlertAction.init(title: "取消", style: .default, handler: { (action) in})
let alertAction1 = UIAlertAction.init(title: "确定(\(countdown))", style: .default, handler: { (action) in
    //确定的操作
})
alertVc.addAction(alertAction1)
alertVc.addAction(alertAction0)
weakSelf?.present(alertVc, animated: true, completion: {
})
if countdown != 0 {
    let queue: DispatchQueue = DispatchQueue.global()
    let countdownTimer = DispatchSource.makeTimerSource(flags: [], queue: queue)
    countdown = countdown + 1
    countdownTimer.scheduleRepeating(deadline: .now(), interval: .seconds(1))
    countdownTimer.setEventHandler(handler: {
        countdown = countdown - 1
        if countdown <= 0 {
            countdownTimer.cancel()
            DispatchQueue.main.async {
                alertAction1.setValue("确定(0)", forKey: "title")
                alertAction1.setValue(UIColor.hrgb("CCCCCC"), forKey: "titleTextColor")
                alertAction1.isEnabled = false
                // message
                let one: NSString = "\(title)\n\(time)\n" as NSString
                let two: NSString = "\(timeout)" as NSString
                let message = "\(title)\n\(time)\n\(timeout)"
                let alertControllerMessageStr = NSMutableAttributedString(string: message)
                alertControllerMessageStr.addAttribute(NSForegroundColorAttributeName, value: UIColor.hrgb("DF503C"), range: NSMakeRange(one.length, two.length))
                alertControllerMessageStr.addAttribute(NSFontAttributeName, value: UIFont.systemFont(ofSize: 13), range: NSMakeRange(one.length, two.length))
                alertVc.setValue(alertControllerMessageStr, forKey: "attributedMessage")
            }
        }else {
            DispatchQueue.main.async {
                alertAction1.setValue("确定(\(countdown))", forKey: "title")
            }
        }
    })
    countdownTimer.resume()
}