iphone - 如何在 Swift 中使用警报 View 解除 segue？

Question

我有几个 View Controller 。如果 Alert View 被确认，我需要返回到第一个 View Controller。如果没有 unwind Segue，我会这样做:

@IBAction func unwindToDelete ( segue: UIStoryboardSegue ) {

    let alertView = UIAlertController(title: "Delete?", message: "Are you sure you wante to delete?", preferredStyle: .ActionSheet)

    let deleteAction = UIAlertAction (title: "Delete", style: .Destructive ) { alertAction in

        self.deleteChoice = true
    }

    let cancelAction = UIAlertAction (title: "Cancel", style: .Cancel ) {  alertAction in

    }

    alertView.addAction(deleteAction)
    alertView.addAction(cancelAction)

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

}

但如果我这样做，在这段代码中它会因为最后一行代码而崩溃。

这是错误:

2015-04-30 14:59:45.605 PhotosCollection[4624:182995] 
popToViewController:transition: called on <UINavigationController 0x7a67aeb0> 
while an existing transition or presentation is occurring; the navigation 
stack  will not be updated. 

如何在能够解除 segue 的同时完成警报 View 。

谢谢

Answer 1

您是在解除操作发生后发出警报。如果用户选择取消删除，您希望能够完全不执行展开。我建议如下:

1. 不要将 unwind segue 连接到您的删除按钮，而是将它连接到 View Controller 顶部的 View Controller 图标，以便您可以以编程方式调用 unwind。这个答案告诉你如何做到这一点: Setting up the unwind segue .为 unwind segue 提供一个标识符，例如 "doUnwind"。

2. 在您的删除按钮的 @IBAction 中，发出警告，询问用户是否真的要删除。

3. 在删除按钮的处理程序中，以编程方式调用展开转场。

       @IBAction func deleteButton (button: UIButton) {
   
           let alertView = UIAlertController(title: "Delete?", message: "Are you sure you wante to delete?", preferredStyle: .ActionSheet)
   
           let deleteAction = UIAlertAction (title: "Delete", style: .Destructive ) { alertAction in
   
                self.performSegueWithIdentifier("doUnwind", sender: self)
           }
   
           let cancelAction = UIAlertAction (title: "Cancel", style: .Cancel ) {  alertAction in
   
           }
   
           alertView.addAction(deleteAction)
           alertView.addAction(cancelAction)
   
           self.presentViewController(alertView, animated: true, completion: nil)
   
       }