Navigation

Hyperdrive view model navigation uses a tree-like structure instead of Jetpack Compose's NavController path structure.

The view models presented are attached into the navigation tree and their observing in collect as well as any work in whileAttached() is performed.

[TODO: Hyperdrive navigation is being upgraded to support jumping to a specific node in the tree (e.g. user detail with an ID from a notification).]

The parent view model presents the child view models and has full control over whether they're shown or not:

EventListViewModel.kt

class EventListViewModel: BaseViewModel() {    var presentedDetail: EventDetailViewModel? by managed(null)
    fun openDetail() {        presentedDetail = EventDetailViewModel()    }}

In SwiftUI, it's enough to use SwitchingNavigationLink with the presented view model as its parameter along with the content that represents the view to present.

EventListView.swift

struct EventListView: View {    @ObservedObject    private(set) var viewModel: EventListViewModel
    var body: some View {        NavigationView {            ZStack {                SwitchingNavigationLink(                    selection: $viewModel.presentedDetail,                    content: { EventDetailView(viewModel: $0) }                )
                // View layout.            }        }    }

Jetpack Compose doesn't use NavController and instead Hyperdrive's NavigationController is utilized.

EventListView.kt

@Composablefun EventListView(viewModel: EventListViewModel, modifier: Modifier) {    if (viewModel.presentedDetail == null) {        // View layout.    }
    NavigationController.Pushed(present = viewModel::presentedDetail) {        EventListView(viewModel = it, modifier = modifier)    }}

The current view is shown if presentedDetail is null, otherwise NavigationController automatically presents the provided view.