Question

我有几个视图控制器。如果确认了警报视图，我需要返回第一个View Controller。如果没有放松塞格，我就会这样做：

@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)

}

但是，如果我这样做，在这段代码中它会崩溃，因为最后一行代码。

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.

如何在能够解开segue的同时完成警报视图。

谢谢

Answer 1

放松后你正在发出警报。如果用户选择取消删除，您希望根本不能执行展开。我建议如下：

而不是将展开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。这个答案告诉你如何做到这一点： Setting up the unwind segue。给展开segue一个标识符，例如"doUnwind"。
在删除按钮的@IBAction中，提出警告，询问用户是否确实要删除。

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)

    }

如何在Swift中使用警报视图展开segue？

1 个答案: