1.新建一个消息弹窗方法，弹窗标题"错误!",关闭弹窗按钮是“好的”

    func showMsgbox(_message: String, _title: String = "错误!") {
        let alert = UIAlertController(title: _title, message: _message, preferredStyle: UIAlertController.Style.alert)
        let btnOK = UIAlertAction(title: "好的", style: .default, handler: nil)
        alert.addAction(btnOK)
        self.present(alert, animated: true, completion: nil)
    } 

2.调用自定义弹窗函数

showMsgbox(_message: "弹窗里要显示的内容")