Question

当用户触摸“开始”以启动计时器时，我一直尝试弹出警报消息，当任何或所有3个所需文本字段为空时。模拟器中没有弹出警告信息。

@IBAction func start(_ sender: Any) {
//the following code produces an alert if any of the specified text fields are blank when the "start" button is pressed
if medName.text == nil || dose.text == nil || freq.text == nil {

    let alertController = UIAlertController(title: "Field(s) must be filled in!", message: "Please complete all fields.", preferredStyle: UIAlertControllerStyle.alert)

    alertController.addAction(UIAlertAction(title: "OK", style: .default, handler: { (action)
        in
        self.dismiss(animated: true, completion: nil)}))

    self.present(alertController, animated: true, completion: nil)

    } else {

        timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(SecondViewController.decreaseTimer), userInfo: nil, repeats: true)

    let itemsObject = UserDefaults.standard.object(forKey: "cellContent")

    var cellContent:[String]

    if let tempItems = itemsObject as? [String] {

        cellContent = tempItems

        cellContent.append(medName.text!)

    } else {

        cellContent = [medName.text!]

    }

    UserDefaults.standard.set(cellContent, forKey: "cellContent")
    //the following code clears the text within each of the specified text fields when start is pressed
    medName.text = ""
    dose.text = ""
    freq.text = ""
    }
}

Answer 1

文本字段不是 nil，当它为空且没有文本时，这就是您不输入if语句的原因。这样做会检查您的文本是""：

if medName.text == "" || dose.text == "" || freq.text == ""

警报消息无法显示

1 个答案: