swift 3.0 实现短信验证码倒计时功能

classTCCountDown {

privatevar countdownTimer: Timer?

var codeBtn = UIButton()

privatevar remainingSeconds: Int =0{

  willSet {

    codeBtn.setTitle("重新获取(newValue)秒",for: .normal)

    ifnewValue <=0{

      codeBtn.setTitle("获取验证码",for: .normal)

      isCounting =false

    }

  }

}

var isCounting =false{

  willSet {

    ifnewValue {

      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

  }

}

@objcprivatefunc updateTime() {

  remainingSeconds -=1

}

 }

 //调用方法

 var countDown = TCCountDown()//实例化

 countDown.isCounting =true//开启倒计时