var sendButton: UIButton!

override func viewDidLoad() {
    super.viewDidLoad()

    sendButton = UIButton()
    sendButton.frame = CGRect(x: 40, y: 100, width: view.bounds.width - 80, height: 40)
    sendButton.backgroundColor = UIColor.redColor()
    sendButton.setTitleColor(UIColor.whiteColor(), forState: .Normal)
    sendButton.setTitle("獲取驗證碼", forState: .Normal)
    sendButton.addTarget(self, action: "sendButtonClick:", forControlEvents: .TouchUpInside)

    self.view.addSubview(sendButton)
}

var remainingSeconds = 0

var remainingSeconds: Int = 0 {
    willSet {
        sendButton.setTitle("驗證碼已發送(/(newValue)秒后重新獲取)", forState: .Normal)

        if newValue <= 0 {
            sendButton.setTitle("重新獲取驗證碼", forState: .Normal)
            isCounting = false
        }
    }
}

var countdownTimer: NSTimer?

var isCounting = false {
    willSet {
        if newValue {
            countdownTimer = NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: "updateTime", userInfo: nil, repeats: true)

            remainingSeconds = 10
            sendButton.backgroundColor = UIColor.grayColor()
        } else {
            countdownTimer?.invalidate()
            countdownTimer = nil

            sendButton.backgroundColor = UIColor.redColor()
        }

        sendButton.enabled = !newValue
    }
}

func updateTime(timer: NSTimer) {
     // 計時開始時，逐秒減少remainingSeconds的值
    remainingSeconds -= 1
}

 func sendButtonClick(sender: UIButton) {
    // 啟動倒計時
    isCounting = true
}