Recursive NavigationStack? → stuck at level 2?

Hi, I wanted to detect that a NavigationLink was selected, so I wrote a ViewModifier using list($selection:) and navigationDestination(isPresent:).

If you are not using $path in your NavigationStack(path:), you might be able to use this ViewModifier idea for data loading with onChange(of: selection) {}.

I attach below the sample code for a recursive FileListViewer.

You can get this ViewModifier and other sample code from https://github.com/hmuronaka/NavigationDestinationSelectedViewModifier.

I hope this idea will be helpful to you.

import SwiftUI
import NavigationDestinationSelectedViewModifier

struct PlainFileList2<Destination: View>: View {
    let current: URL
    let paths: [URL]

    @ViewBuilder let destination: (URL) -> Destination
    @State private var selection: URL?
    @State private var childPaths: [URL]?

    var body: some View {
        List(selection: $selection) {
            ForEach(paths, id: \.self) { url in
                if FileManager.default.isDirectory(url: url) {
                    NavigationLink(value: url) {
                        Label(url.lastPathComponent, systemImage: "folder")
                    }
                } else {
                    self.destination(url)
                }
            }
        }
        .navigationDestination(selection: $selection, item: $childPaths ) { childPaths in
            if let selection {
                PlainFileList2(current: selection, paths: childPaths, destination: self.destination)
            }
        }
        .onChange(of: selection, perform: { newValue in
            if let newValue, FileManager.default.isDirectory(url: newValue) {
                self.childPaths = try! FileManager.default.contentsOfDirectory(at: newValue, includingPropertiesForKeys: [.parentDirectoryURLKey, .creationDateKey, .fileSizeKey], options: [])
            } else {
                self.childPaths = nil
            }
        })
        .navigationTitle(current.lastPathComponent)
    }
}

ViewModifier

import SwiftUI

fileprivate struct NavigationDestinationViewModifier<SelectionValue: Hashable, Value: Equatable, Destination: View>: ViewModifier {
   
    @Binding var selection: SelectionValue?
    @Binding var item: Value?
    @ViewBuilder let destination: (Value) -> Destination

    func body(content: Content) -> some View {
        content
            .navigationDestination(isPresented: .init(get: {
                item != nil
            }, set: { newValue in
                if !newValue {
                    item = nil
                }
            })) {
                if let selected = item {
                    destination(selected)
                } else {
                    EmptyView()
                }
            }
            .onChange(of: item) { newValue in
                if newValue == nil && selection != nil {
                    selection = nil
                }
            }
    }
}

public extension View {
    func navigationDestination<SelectionValue: Hashable, Value: Equatable, Destination: View>(selection: Binding<SelectionValue?>, item: Binding<Value?>, @ViewBuilder destination: @escaping (Value) -> Destination) -> some View {
        return self.modifier(NavigationDestinationViewModifier(selection: selection, item: item, destination: destination))
    }
}

If you simply want to be able to recurse, the following code might work.

NavigationStack {
   RecursiveView (rootItemList)
     .navigationDestination(for: Item.self) { item in
       RecursiveView(item.childList)
     }
}

struct RecursiveView (itemList) {
  List {
    ForEach (item in itemList) {
      if item.isLeaf {
        someView (item)
      } else {
         NavigationLink(value: item) { label(item) }
    }
  }
}

Thanks a bunch!

I ended up adopting an entirely different tactics (I wrote an OutlineGroup-like widget where I have individual control over the state of the different DisclosureGroups – to be more precise, there isn't even a single DisclosureGroup involved in it, but it looks like if). However, I’ll be storing your code for future use!

Once again, thanks so much for answering!