How to get the last two items from the stack of a NavigationPath() object

Question

Created Mar ’24

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I am facing a challenge in SwiftUI and would appreciate some guidance. In my code, I'm working with a NavigationPath() object and need to obtain the last two items from the stack by using the properties of this object. Specifically, this operation should occur within a view named SomeView, which is deep in the navigation stack.

Inside the action closure of a Button within SomeView, I want to assign the last two items of the navigationControl.path to a let constant if they exist.

I've scoured various sources for a solution, but unfortunately, I haven't found one that fits my requirements. It is crucial that the last two items are obtained from the navigationControl variable retrieved from the environment. While I am aware that these items can be obtained by injecting them into SomeView during its instantiation at the parent view, this approach is not acceptable in my case.

To provide a comprehensive overview of the project, I've attached relevant code snippets from other files as well.

//  SomeView.swift

import SwiftUI

struct SomeView: View {
    @Environment(NavigationControl.self) private var navigationControl: NavigationControl
    
    var body: some View {
        Button("Tap to get the last two items in NavigationStack") {
            // Not sure what to write here.
            // It must be something like the following options just to illustrate what is desired:
            // let lastItem = navigationControl.path.last()
            // let lastItem = navigationControl.path[navigationControl.path.count]
            // However, neither of them are defined.
            // Note that only the last item assignemnt is shown here. However, it is desired to get the last two items from path.
        }
    }
}

#Preview {
    NavigationStack {
        SomeView()
            .environment(NavigationControl())
    }
}

//  NavigationControl.swift

import SwiftUI

@Observable class NavigationControl {
    var path = NavigationPath()
}

//  ContentView.swift

import SwiftUI

struct ContentView: View {
    @Environment(NavigationControl.self) private var navigationControl: NavigationControl
    var body: some View {
        @Bindable var navigationControl = navigationControl
        NavigationStack(path: $navigationControl.path)
        {
            Button("Navigate") {
                for i in 1..<5 {
                    navigationControl.path.append(i)
                }
            }
            .navigationTitle("Root View")
            .navigationDestination(for: Int.self) { number in
                SomeView()
            }
        }
    }
}

#Preview {
    NavigationStack {
        ContentView()
            .environment(NavigationControl())
    }
}


//  NavigationPathLastElementApp.swift

import SwiftUI

@main
struct NavigationPathLastElementApp: App {
    @State var navigationControl = NavigationControl()
    var body: some Scene {
        WindowGroup {
            ContentView()
                .environment(navigationControl)
        }
    }
}

Any insights or suggestions on how to achieve this would be highly appreciated. Many thanks in advance for your assistance!

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Answer 1

Vision Pro Engineer OP

Apple

Mar ’24

Hi @canbaltaci ,

Are you able to use an array of a type instead of the type-erased NavigationPath? If you're able to use something like [Int] as the path, then you could do this in the button:

 Button("Tap to get the last two items in NavigationStack") {
            let lastTwoItems = navigationControl.path.suffix(from: navigationControl.path.count - 2)
            print(lastTwoItems)
}

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