func showMsgbox(_message: String, _title: String = "提示"){
        
        let alert = UIAlertController(title: _title, message: _message, preferredStyle: UIAlertControllerStyle.alert)
        let btnOK = UIAlertAction(title: "好的", style: .default, handler: nil)
        alert.addAction(btnOK)
        self.present(alert, animated: 
 
true, completion: nil)
        
    }
    
    @IBAction func btnLoginClick(_ sender: Any) {

if tvName.text == ""{

showMsgbox(_message: "請輸入帳號")

return

}

if tvPassword.text == ""{

showMsgbox(_message: "請輸入密碼")

return

}

    }

swift 彈出提示框