class TCCountDown {
private var countdownTimer: Timer?
var codeBtn = UIButton()
private var remainingSeconds: Int = 0 {
    willSet {
        codeBtn.setTitle("重新獲取\(newValue)秒", for: .normal)

        if newValue <= 0 {
            codeBtn.setTitle("獲取驗證碼", for: .normal)
            isCounting = false
 

        }
    }
}
var isCounting = false {
    willSet {
        if newValue {
            countdownTimer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(self.updateTime), userInfo: nil, repeats: true)

            remainingSeconds = 60
            codeBtn.setTitleColor(BtnCodeColor
 
, for: .normal)
        } else {
            countdownTimer?.invalidate()
            countdownTimer = nil

            codeBtn.setTitleColor(MainColor, for: .normal)
        }

        codeBtn.isEnabled = !newValue
    }
}
@objc private func updateTime() {
    remainingSeconds -= 1
}
  }
  //呼叫方法
  var
 
 countDown = TCCountDown()//例項化
  countDown.isCounting = true//開啟倒計時