从Swift中的导航后退按钮展开segue [英] Unwind segue from navigation back button in Swift

问题描述

我有一个设置屏幕，因为我有一个表格单元格。通过单击我进入另一个屏幕，用户可以选择一个选项，并在按下后退按钮时将其返回到上一个视图控制器。

I have a settings screen, in that I have a table cell. By clicking on that I take to another screen where user can choose an option and I want it back in the previous view controller when back button is pressed.

我可以放置一个自定义栏按钮项，但我想使用导航栏中的后退按钮返回到父视图控制器，而不是在视图上使用自定义按钮。

I can put a custom bar button item, but I want to return to the parent view controller using the back button in the navigation bar rather than with a custom button on the view.

我似乎无法覆盖导航后退按钮，将其指向我的展开segue操作，因为后面故事板上没有出现按钮，我无法将绿色的退出按钮拖到它上面

I don't seem to be able to override the navigation back button to point it down to my unwind segue action and since the back button doesn't appear on the storyboard, I cant drag the green Exit button to it

是否可以使用后退按钮展开推送segue？

Is it possible to unwind a push segue with the back button?

推荐答案

这是我的解决方案，基于Blankarsch的Objective-C代码到此StackOverflow问题：如何捕获后退按钮事件

Here's my solution, based on Objective-C code from Blankarsch to this StackOverflow question: How to trap the back button event

将此代码放入View Controller中，您想要捕获Back按钮调用：

Put this code inside the View Controller you want to trap the Back button call from:

override func didMoveToParentViewController(parent: UIViewController?) {
    if (!(parent?.isEqual(self.parentViewController) ?? false)) {
        println("Back Button Pressed!")
    }
}

在if块的内部，处理你需要传回的任何内容。您还需要有一个返回调用视图控制器的引用，因为此时很可能parent和self.parentViewController都是nil，因此您无法导航View Controller树。

Inside of the if block, handle whatever you need to pass back. You'll also need to have a reference back to calling view controller as at this point most likely both parent and self.parentViewController are nil, so you can't navigate the View Controller tree.

此外，您可以通过简单地检查父项为nil来逃避，因为我没有找到按下后退按钮不会导致父项为零的情况。所以这样的事情更简洁：

Also, you might be able to get away with simply checking parent for nil as I haven't found a case where pressing the back button didn't result in parent being nil. So something like this is a bit more concise:

override func didMoveToParentViewController(parent: UIViewController?) {
    if (parent == nil) {
        println("Back Button Pressed!")
    }
}

但我不能保证每次都会有效。

But I can't guarantee that will work every time.

Andrew

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