按下按钮后UIAlert验证中的Swift3 UITextField

我已经用两个文本字段实现了警报窗口。我想执行一些验证：如果其中一个文本字段为空（用户没有输入任何值），应用程序不应该允许用户按下“完成”按钮。 我不想显示任何警报，只想不允许用户保存空白数据

我已经创建了下面列出的函数。增加了两名后卫。但在这种情况下，若用户并没有输入任何内容，警报就会关闭，并且不会保存任何内容。我不希望警报窗口关闭

如果可以，怎么办？我还没有找到答案。我已经检查了这个问题，但看起来它不适合我。谢谢你的帮助

private func addTable() {
    let alert = UIAlertController(title: NSLocalizedString("inputTableParams", comment: ""), message: nil, preferredStyle: .alert)
    alert.addTextField(configurationHandler: configureTableNameTextField)
    alert.addTextField(configurationHandler: configureTableCapacityTextField)
    alert.textFields?[0].autocapitalizationType = .sentences
    alert.textFields?[1].autocapitalizationType = .sentences
    alert.addAction(UIAlertAction(title: NSLocalizedString("alertCancel", comment: ""), style: .cancel, handler: nil))
    alert.addAction(UIAlertAction(title: NSLocalizedString("alertDone", comment: ""), style: .default, handler: { (UIAlertAction) in
        guard self.tableNameTextField.text != "" else {return}
        guard self.tableCapacityTextField.text != "" else {return}
        let newTable = Table(tableName: self.tableNameTextField.text!, tableCapacity: Int(self.tableCapacityTextField.text!)!)
        let result = try? TablesTable.getOrCreateTable(table: newTable)
        if result != nil {
            self.updateTableView()
        }
    }))
    self.present(alert, animated: true, completion: {})
}

---

看起来不可能完全按照我的要求执行，因此我实现了另一个带有错误的警报窗口

//MARK: Functions
//Functions for Alert window for adding table
private func configureTableNameTextField (textField: UITextField!) {
    textField.placeholder = NSLocalizedString("tableName", comment: "")
    textField.keyboardType = .default
    tableNameTextField = textField
}
private func configureTableCapacityTextField (textField: UITextField!) {
    textField.placeholder = NSLocalizedString("tableCapacity", comment: "")
    textField.keyboardType = .numberPad
    tableCapacityTextField = textField
}

private func showAlertParamsNotFilledProperly() {
    let alertNoCanDo = UIAlertController(title: NSLocalizedString("alertNoCanDo", comment: ""), message: NSLocalizedString("paramsNotFilledProperly", comment: ""), preferredStyle: .alert)
    alertNoCanDo.addAction(UIAlertAction(title: NSLocalizedString("alertDone", comment: ""), style: .cancel, handler: nil))
    self.present(alertNoCanDo, animated: true, completion: {})
}

private func showAlertUnableToSave() {
    let alertNoCanDo = UIAlertController(title: NSLocalizedString("alertUnableToSaveData", comment: ""), message: NSLocalizedString("checkInputParameters", comment: ""), preferredStyle: .alert)
    alertNoCanDo.addAction(UIAlertAction(title: NSLocalizedString("alertDone", comment: ""), style: .cancel, handler: nil))
    self.present(alertNoCanDo, animated: true, completion: {})
}

//Functions for managing tables
private func addTable() {
    let alert = UIAlertController(title: NSLocalizedString("inputTableParams", comment: ""), message: nil, preferredStyle: .alert)
    alert.addTextField(configurationHandler: configureTableNameTextField)
    alert.addTextField(configurationHandler: configureTableCapacityTextField)
    alert.textFields?[0].autocapitalizationType = .sentences
    alert.textFields?[1].autocapitalizationType = .sentences
    alert.addAction(UIAlertAction(title: NSLocalizedString("alertCancel", comment: ""), style: .cancel, handler: nil))
    alert.addAction(UIAlertAction(title: NSLocalizedString("alertDone", comment: ""), style: .default, handler: { (UIAlertAction) in
        if self.tableNameTextField.text == "" || self.tableCapacityTextField.text == "" {
            self.showAlertParamsNotFilledProperly()
            return
        }
        if let number = NumberFormatter().number(from: self.tableCapacityTextField.text!) {
            let capacity = Int(number)
            let newTable = Table(tableName: self.tableNameTextField.text!, tableCapacity: capacity)
            let result = try? TablesTable.getOrCreateTable(table: newTable)
            if result != nil {
                self.updateTableView()
            }
        } else {
            self.showAlertParamsNotFilledProperly()
            return
        }
    }))
    self.present(alert, animated: true, completion: {})
}