警报框未显示。 X 代码是跳过 Swift 中的警报框代码

Question

当我在ViewController2 中performSegue 然后在ViewController1 中自动调用unwindToMyHours。 那么我不知道为什么 X Code 会跳过呈现Alert BOX 的代码。

OUTPUT -> 其他部分完成。

和 xCode 跳过 -> Task 1 和 task 2

~ViewController2的代码

@IBAction func CancelButtonTapped(_ sender: UIButton) {
    let alert = UIAlertController(title: "Delete Time", message: "Are you sure?", preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "Delete", style: .destructive, handler: { [self] _ in
            
            self.deleted = true
            self.performSegue(withIdentifier: "unwindToMyHours", sender: nil)
        }))
        alert.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: nil))
        self.present(alert, animated: true, completion: nil)
 }

~ViewController1的代码

@IBAction func unwindToMyHours( _ seg: UIStoryboardSegue) {
    if (seg.source as? ViewController2)?.submitted == true {
        loadData()
    } else if (seg.source as? ViewController2)?.deleted == true {
        let alert = UIAlertController(title: "Deleted", message: "Tabel have been updated", preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "OK", style: .default, handler: { alert in
            print("Task 1")
        }))
        present(alert, animated: true) {
            print("Task 2")
        }
        print("Else part complete")
    }
}

Answer 1

嗯。 也许您忘记销毁您的第一个警报控制器。

在不破坏第一个警报控制器的情况下，您呈现第二个警报控制器，因此 XCode 无法呈现您的第二个警报控制器。

你的代码看起来不错……让我编辑一下。

~ViewController2的代码

@IBAction func CancelButtonTapped(_ sender: UIButton) {
    let alert = UIAlertController(title: "Delete Time", message: "Are you sure?", preferredStyle: .alert)
    alert.addAction(UIAlertAction(title: "Delete", style: .destructive, handler: { [self] _ in
        
        self.deleted = true
        self.dismiss(animated: false, completion: nil) // You are forgetting  this
        self.performSegue(withIdentifier: "unwindToMyHours", sender: nil)
    }))
    alert.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: nil))
    self.present(alert, animated: true, completion: nil)
}

---

~ViewController1 的代码 -> 相同的代码

@IBAction func unwindToMyHours( _ seg: UIStoryboardSegue) {
if (seg.source as? ViewController2)?.submitted == true {
    loadData()
} else if (seg.source as? ViewController2)?.deleted == true {
    let alert = UIAlertController(title: "Deleted", message: "Tabel have been updated", preferredStyle: .alert)
    alert.addAction(UIAlertAction(title: "OK", style: .default, handler: { alert in
        print("Task 1")
    }))
    present(alert, animated: true) {
        print("Task 2")
    }
    print("Else part complete")
}
}

Answer 2

这很可能是因为您之前的视图控制器还没有被解雇，并且您不能present 一个新的视图控制器（警报是），直到您的视图控制器成为顶部。等到发生这种情况：

var shouldDisplayDeletedAlert = false

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    if shouldDisplayDeletedAlert {
        let alert = UIAlertController(title: "Deleted", message: "Tabel have been updated", preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "OK", style: .default, handler: { alert in
            print("Task 1")
        }))
        present(alert, animated: true) {
            print("Task 2")
        }
        shouldDisplayDeletedAlert = false
    }
}

@IBAction func unwindToMyHours( _ seg: UIStoryboardSegue) {
    if (seg.source as? ViewController2)?.submitted == true {
        loadData()
    } else if (seg.source as? ViewController2)?.deleted == true {
        shouldDisplayDeletedAlert = true
    }
}