Ios 在某些情况下如何取消一个序列（如果/否则）？

我正在创建一个应用程序。在某个视图中，有几个文本字段，用户在其中输入数字，然后按下按钮，然后传输到下一个视图控制器

如果一个人点击按钮，一个或多个文本字段为空，segue将取消，该如何设置

以下是我迄今为止在该领域的代码：

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    if saveButton === sender {
        let name = nameTextField.text ?? ""

        // Set the meal to be passed to MealListTableViewController after the unwind segue.
        meal = Meal(name: name)

    }

   if calcButton === sender {

    if weightInKilos.text == "" && percentOfDehydration.text == "" && ongoingLosses.text == "" && factor.text == "" {

        let alertController = UIAlertController(title: "Fields were left empty.", message:
            "You left some fields blank! Please make sure that all fields are filled in before tapping 'Calculate'.", preferredStyle: UIAlertControllerStyle.Alert)
        alertController.addAction(UIAlertAction(title: "Dismiss", style: UIAlertActionStyle.Default,handler: nil))

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

    }

    else {
        let DestViewController: ftrViewController = segue.destinationViewController as! ftrViewController

        let weightInt: Int? = Int(weightInKilos.text!)
        let dehydrationInt: Int? = Int(percentOfDehydration.text!)
        let lossesInt: Int? = Int(ongoingLosses.text!)
        let factorInt: Int? = Int(factor.text!)

        let lrs24Int = (30 * weightInt! + 70) * factorInt! + weightInt! * dehydrationInt! * 10 + lossesInt!

        let lrsPerHourint = lrs24Int / 24

        DestViewController.lrsHr = "\(lrsPerHourint)"
        DestViewController.lrs24Hrs = "\(lrs24Int)"
    }
    }
}

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在打电话给segue之前，你必须检查你需要的一切

所以，用户写下答案，你检查是否一切正常，如果一切正常，继续，否则，你通知用户并要求重新键入信息

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明白了吗？

哪里有运行

performsgue的代码，或者您是直接在情节提要中执行的？使用函数shoulderforsegue，它返回一个bool，指示是否应该执行segue