问题描述

这已在 iOS 13.3 中修复！

最小的可重现示例(Xcode 11.2 beta，适用于 Xcode 11.1):

Minimal reproducible example (Xcode 11.2 beta, this works in Xcode 11.1):

struct Parent: View {
    var body: some View {
        NavigationView {
            Text("Hello World")
                .navigationBarItems(
                    trailing: NavigationLink(destination: Child(), label: { Text("Next") })
                )
        }
    }
}

struct Child: View {
    @Environment(.presentationMode) var presentation
    var body: some View {
        Text("Hello, World!")
            .navigationBarItems(
                leading: Button(
                    action: {
                        self.presentation.wrappedValue.dismiss()
                    },
                    label: { Text("Back") }
                )
            )
    }
}

struct ContentView: View {
    var body: some View {
        Parent()
    }
}

问题似乎在于将我的 NavigationLink 放在 navigationBarItems 修饰符中，该修饰符嵌套在根视图为 NavigationView.崩溃报告表明，当我向前导航到 Child 然后返回到 Parent 时，我正在尝试弹出一个不存在的视图控制器.

The issue seems to lie in placing my NavigationLink inside of a navigationBarItems modifier that's nested inside of a SwiftUI view whose root view is a NavigationView. The crash report indicates that I'm trying to pop to a view controller that doesn't exist when I navigate forward to Child and then back to Parent.

Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Tried to pop to a view controller that doesn't exist.'
*** First throw call stack:

如果我改为将 NavigationLink 放在视图主体中，如下所示，它工作得很好.

If I were to instead place that NavigationLink in the body of the view like the below, it works just fine.

struct Parent: View {
    var body: some View {
        NavigationView {
            NavigationLink(destination: Child(), label: { Text("Next") })
        }
    }
}

这是 SwiftUI 错误还是预期行为?

Is this a SwiftUI bug or expected behavior?

我已经在他们的反馈助手中打开了 Apple 的问题，ID 为 FB7423964，以防 Apple 的任何人关心:).

I've opened an issue with Apple in their feedback assistant with the ID FB7423964 in case anyone out there from Apple cares to weigh in :).

我在反馈助手中打开的工单表明有 10 多个类似的报告问题.他们已使用 Resolution:Potential fix known - For a future OS update 更新了该解决方案.手指交叉，修复很快就会着陆.

My open ticket in the feedback assistant indicates there are 10+ similar reported issues. They've updated the resolution with Resolution: Potential fix identified - For a future OS update. Fingers crossed that the fix lands soon.

推荐答案

这对我来说是个痛点！我离开了它，直到我的大部分应用程序完成并且我有足够的空间来处理崩溃.

This was quite a pain point for me! I left it until most of my app was completed and I had the mind space to deal with the crashing.

我想我们都同意 SwifUI 有一些非常棒的东西，但调试可能很困难.

I think we can all agree that there's some pretty awesome stuff with SwifUI but that the debugging can be difficult.

在我看来，我会说这是一个BUG.这是我的理由:

In my opinion, I would say that this is a BUG. Here is my rationale:

• 如果你将presentationModedismiss调用包裹在大约半秒的异步延迟中，你应该会发现程序将不再崩溃.

• If you wrap the presentationMode dismiss call in an asynchronous delay of about a half-second, you should find that the program will no longer crash.

DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
    self.presentationMode.wrappedValue.dismiss()
}