Question

我有一个带有4个UITextField的应用程序，如果UITextfield为空，我想显示一个UIAlert。我具有选择显示的UIAlert的功能，如下所示：

func displayMyAlertMessage(userMessage: String) {
    let myAlert = UIAlertController(title: "Alert", message: userMessage, preferredStyle: UIAlertController.Style.alert)
    let okAction = UIAlertAction(title: "Ok", style: UIAlertAction.Style.default, handler: nil)
    myAlert.addAction(okAction)
    self.present(myAlert, animated: true, completion: nil)
}

我已经看过这个example了，因为我有UIPickerView来显示文本，所以无法使它工作。下面是我的didSelectRow代码：

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {

    if TrackTextField.isFirstResponder {
        selectedTrack = tracks[row]
        guard let track = selectedTrack?.isEmpty else {
            displayMyAlertMessage(userMessage: "You have to fill in a track")
            return
        }
        TrackTextField.text = String(track)
    } else if firstTextField.isFirstResponder {
        firstDriver = drivers[row]
        firstTextField.text = firstDriver
    } else if secondTextField.isFirstResponder {
        secondDriver = drivers[row]
        secondTextField.text = secondDriver
    } else if thirdTextField.isFirstResponder {
        thirdDriver = drivers[row]
        thirdTextField.text = thirdDriver
    }
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "getPredictor" {
        let predictorVC = segue.destination as! UINavigationController
        let vc = predictorVC.topViewController as! PredictorTableViewController
        self.grandPrix.append(GrandPrix(granPrix: TrackTextField.text!, firstDriver: firstTextField.text!, secondDriver: secondTextField.text!, thirdDriver: thirdTextField.text!))
        vc.grandPrix = self.grandPrix


    }
}

我已经使用TrackTextField来测试警报是否起作用。当我单击Grandprix Predictor时，不会出现UIAlert。下面是与下一个UIViewController关联的函数。

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "getPredictor" {
        let predictorVC = segue.destination as! UINavigationController
        let vc = predictorVC.topViewController as! PredictorTableViewController
        self.grandPrix.append(GrandPrix(granPrix: TrackTextField.text!, firstDriver: firstTextField.text!, secondDriver: secondTextField.text!, thirdDriver: thirdTextField.text!))
        vc.grandPrix = self.grandPrix


    }

任何帮助将不胜感激。

Answer 1

不应在选择器视图委托中进行检查。

答案实际上取决于您甚至想用来触发检查的内容。在用户应该填写所有四个文本字段之后，最有可能要在单击某些按钮时进行检查。

添加一个verifyInput方法。像这样：

func verifyInput() -> Bool {
    if TrackTextField.text?.isEmpty || firstTextField.text?.isEmpty || secondTextField.text?.isEmpty || thirdTextField.text?.isEmpty {
        // at least one is empty, show your alert here
        return false
    } else {
        return true // all good
    }
}

然后从某个按钮处理程序或也许从verifyInput调用shouldPerformSegue。同样，这取决于您要用来触发检查的事件。

示例：

override func shouldPerformSegue(withIdentifier identifier: String, sender: Any?) -> Bool {
    // Only validate for this specific segue
    if identifier == "getPredictor" {
        return verifyInput()
    } else {
        return true
    }
}

根据需要调整逻辑。

如果UITextField为空白，则不会出现UIAlert

1 个答案: