Multiple NavigationStack In NavigationSplitView Issue

Question

Created Sep ’22

Replies 1

Boosts 0

Views 1k

Participants 2

I have an app using an NavigationSplitView with a list on the left and detail views on the right. When I select an item from the list on the left, the detail view on the should change and each detail view can push other views. I use a Navigation Stack in each root detail view. The NavigationStack does not seem to be working as expected.

I created a simple example app to show what I am seeing. In the app:

Select Atlantic from the list on the left
Tap on Atlantic View in the detail view to push to Atlantic Pushed View
Select Pacific from the list on the left

The view on the right still shows Atlantic Pushed View when I would expect it to show Pacific View. If on the detail view I tap the back arrow, it goes from Atlantic Pushed View to Pacific View which is not right.

It seems like when I selected Pacific from the left, it replace the root Atlantic view with the root Pacific view in the NavigationStack which is not correct. It also seems like no matter what I try, there is only one NavigationStack path used throughout the app.

The behavior I want and would expect is:

Select Atlantic from the list on the left
Tap on Atlantic View in the detail view to push to Atlantic Pushed View
Select Pacific from the list on the left, which which should show Pacific View
Select Atlantic from the list on the left, which should go back to Pushed Atlantic View

I am considering filing a big report but I wanted to see if I am missing something or is this just not working. My sample code it below.

import SwiftUI

struct Ocean: Identifiable, Hashable {
	let id: String
}

private var oceans = [
	Ocean(id: "Atlantic"),
	Ocean(id: "Pacific"),
]

struct ContentView: View {
	@State var selection: Set<String> = [oceans[0].id]
	
	var body: some View {
		NavigationSplitView {
			List(oceans, selection: $selection) { ocean in
				Text("\(ocean.id) Ocean")
			}
			.navigationTitle("Oceans")
		} detail: {
			if selection.first == "Atlantic" {
				AtlanticView(selection: selection)
			}
			else if selection.first == "Pacific" {
				PacificView(selection: selection)
			}
			else {
				Text("Unknown Ocean")
			}
		}
	}
}

struct AtlanticView: View {
	@State var selection: Set<String>
	@State private var atlanticPath = NavigationPath()
	var body: some View {
		NavigationStack(path: $atlanticPath ) {
			VStack {
				NavigationLink {
					AtlanticPushedView(selection: selection)
				} label: {
					Text("Atlantic View\n\(selection.first!) Ocean")
				}
			}
		}
	}
}

struct AtlanticPushedView: View {
	var selection: Set<String>
	var body: some View {
		Text("Pushed View\n\(selection.first!) Ocean")
	}
}

struct PacificView: View {
	var selection: Set<String>
	@State private var pacificPath = NavigationPath()
	var body: some View {
		NavigationStack(path: $pacificPath ) {
			NavigationLink {
				PacificPushedView(selection: selection)
			} label: {
				Text("Pacific View\n\(selection.first!) Ocean")
			}
		}
	}
}

struct PacificPushedView: View {
	var selection: Set<String>
	var body: some View {
		Text("Pacific Pushed View\n\(selection.first!) Ocean")
	}
}

Boost

Answer 1

carlynorama OP

Oct ’22

I have an example in an unrelated reply (https://developer.apple.com/forums/thread/716804?answerId=731260022#731260022) that does much of what you are trying to do? If I have time I'll try to rework your example code but in the mean time I hope this helps:

Some notes: I'm not sure why your selection is a set of one instead of an Ocean? That is the biggest ?? to me. Are you trying to pass a deep link? In which case why aren't you setting the path with it? If you're trying to manage deep links I'd recommend making a NavigationManager / Coordinator / Store class that lives all the way at the top.

(Ocean will need to be Hashable to use it as an .id() parameter)

struct SplitViewLanding: View {
    var options = ["Alpha", "Beta", "Gamma", "Delta", "Epsilon"]

    //NOTE: the selection binding is an an optional. 
    @State var selection:String?

    var body: some View {
        NavigationSplitView {
            Button("Nil Selection") { selection = nil }
            List(options, id:\.self, selection: $selection) { o in
                Text("\(o)")
            }
        } detail: {
            if let selection {
                RootForDetailView(for: selection).id(selection)
            }

        }
    }
}

class DetailDoNothingVM:ObservableObject {
    @Published var optionSet:String

    deinit {
        print("DetailDoNothingVM DEINIT")
    }

    init() {
        print("DetailDoNothingVM INIT")
        self.optionSet = "Default"
    }

}

struct RootForDetailView: View {
    @StateObject var viewModel = DetailDoNothingVM()
    let optionSet:String

    init(for optionSet:String) {
        self.optionSet = optionSet
    }

    @State var path = NavigationPath()

    let int = Int.random(in: 0...100)

    var body: some View {
        NavigationStack(path: $path) {
            VStack {
                Text("Hello \(int)")
                Button("Go Forward") {
                    path.append(Int.random(in: 0...100))
                }
            }.navigationDestination(for: Int.self) { int in
                DetailOptionIntView(int: int, path: $path).environmentObject(viewModel)
            }.navigationTitle("\(viewModel.optionSet): \(int)")
        }.onAppear() {
            viewModel.optionSet = optionSet
        }
    }
}

struct DetailOptionIntView:View {
    let int:Int
    @Binding var path:NavigationPath
    @EnvironmentObject var viewModel:DetailDoNothingVM

    var body: some View {
        VStack {
            Text("Hello \(int)")
            Button("Go Forward") {
                path.append(Int.random(in: 0...100))
            }
        }.navigationTitle("\(viewModel.optionSet):\(int)")
    }
}

1