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我有几个视图控制器。如果确认警报视图，我需要返回第一个视图控制器。这就是我在没有 unwind Segue 的情况下会做的事情：

@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)

}

但是如果我这样做，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.

如何在能够放松 segue 的同时完成警报视图。

谢谢

4

1 回答 1

10

放松发生后，您将发出警报。如果用户选择取消删除，您希望根本不执行展开。我建议如下：

  1. 不要将展开 segue 连接到删除按钮，而是将其连接到视图控制器顶部的视图控制器图标，以便您可以以编程方式调用展开。这个答案向您展示了如何做到这一点： 设置 unwind segue。给 unwind segue 一个标识符，例如"doUnwind".

  2. 在@IBActionfor your delete 按钮中，提出警告，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 unwind segue。

        @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)

    }
于 2015-04-30T10:34:39.510 回答