Swift3 UITextField在按下按钮后进行UIAlert验证

Question

我已经实现了带有两个文本字段的警报窗口。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），应用程序不应允许用户按“完成”按钮。 我不想显示任何警报，只是不想让用户保存空白数据。

我已经创建了下面列出的功能。增加了两名警卫与回报。但在这种情况下，如果用户没有输入任何内容，则警报会关闭并且不会保存任何内容。我不想让警报窗口关闭。

如果可以做到的话，该怎么办？还没有找到答案。我检查了this的问题，但看起来它不适用于我。感谢你的帮助！

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: {}) 
} 

Answer 1

它看起来不可能做到我想要的，所以我实现了另一个警告窗口，并报错。

//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: {}) 
}