a view stack in the enviroment by value semantic way

ViewStack.swift

@main
struct MyApp: App {
//     @State var viewStack: [ViewStack] = []
    var body: some Scene {
        WindowGroup {
            HomeView()
//                 .environment(\.viewStack, $viewStack)
        }
    }
}
enum ViewStack {
    case scan, timePicker
}
struct ViewStackKey: EnvironmentKey {
    static let defaultValue: Binding<[ViewStack]> = .constant([])
}
extension EnvironmentValues {
    var viewStack: Binding<[ViewStack]> {
        get { self[ViewStackKey.self]           }
        set { self[ViewStackKey.self] = newValue }
    }
}
struct PageView: View {
    @State var viewStack: [ViewStack] = []
    let name: String
    var body: some View {
        VStack(spacing: 10) {
            Text("currentPage: \(name)")
                .padding()
            Text("view stack count: \(viewStack.count)")
            Button(action: { _ = viewStack.popLast() }) {
                Text("back")
            }
            Button(action: { viewStack.append(.timePicker) }) {
                Text("to timePicker")
            }
            Button(action: { viewStack.append(.scan) } ) {
                Text("to scan")
            }
        } .environment(\.viewStack, $viewStack)
    }
}
struct HomeView: View {
    @Environment(\.viewStack) @Binding var viewStack
    var body: some View {
        switch viewStack.last {
        case .scan:
            PageView(name: "scan")
        case .timePicker:
            PageView(name: "timePicker")
        default:
            PageView(name: "Home")
        }
    }
}
struct HomeView_Previews: PreviewProvider {
    static var previews: some View {
        HomeView()
    }
}