SwiftUI problems with Multiplatform NavigationView - swift

Question

I'm currently having all sorts of problems with a NavigationView in my multi-platform SwiftUI app.
My goal is to have a NavigationView with an item for each object in a list from Core Data. And each NavigationLink should lead to a view that can read and write data of the object that it's showing.
However I'm running into many problems, so I figured I'm probably taking the wrong approach.
Here is my code as of now:
struct InstanceList: View {
#StateObject private var viewModel = InstancesViewModel()
#State var selectedInstance: Instance?
var body: some View {
NavigationView {
List {
ForEach(viewModel.instances) { instance in
NavigationLink(destination: InstanceView(instance: instance), tag: instance, selection: $selectedInstance) {
InstanceRow(instance)
}
}
.onDelete { set in
viewModel.deleteInstance(viewModel.instances[Array(set)[0]])
for reverseIndex in stride(from: viewModel.instances.count - 1, through: 0, by: -1) {
viewModel.instances[reverseIndex].id = Int16(reverseIndex)
}
}
}
.onAppear {
selectedInstance = viewModel.instances.first
}
.listStyle(SidebarListStyle())
.navigationTitle("Instances")
.toolbar {
ToolbarItemGroup {
Button {
withAnimation {
viewModel.addInstance(name: "4x4", puzzle: "3x3") // temporary
}
} label: {
Image(systemName: "plus")
}
}
}
}
}
}
and the view model (which probably isn't very relevant but I'm including it just in case):
class InstancesViewModel: ObservableObject {
#Published var instances = [Instance]()
private var cancellable: AnyCancellable?
init(instancePublisher: AnyPublisher<[Instance], Never> = InstanceStorage.shared.instances.eraseToAnyPublisher()) {
cancellable = instancePublisher.sink { instances in
self.instances = instances
}
}
func addInstance(name: String, puzzle: String, notes: String? = nil, id: Int? = nil) {
InstanceStorage.shared.add(
name: name,
puzzle: puzzle,
notes: notes,
id: id ?? (instances.map{ Int($0.id) }.max() ?? -1) + 1
)
}
func deleteInstance(_ instance: Instance) {
InstanceStorage.shared.delete(instance)
}
func deleteInstance(withId id: Int) {
InstanceStorage.shared.delete(withId: id)
}
func updateInstance(_ instance: Instance, name: String? = nil, puzzle: String? = nil, notes: String? = nil, id: Int? = nil) {
InstanceStorage.shared.update(instance, name: name, puzzle: puzzle, notes: notes, id: id)
}
}
and then the InstanceView, which just shows some simple information for testing:
struct InstanceView: View {
#ObservedObject var instance: Instance
var body: some View {
Text(instance.name)
Text(String(instance.id))
}
}
Some of the issues I'm having are:
On iOS and iPadOS, when the app starts, it will show a blank InstanceView, pressing the back button will return to a normal instanceView and pressing it again will show the navigationView
Sometime pressing on a navigationLink will only highlight it and won't go to the destination
On an iPhone in landscape, when scrolling through the NavigationView, sometimes the selected Item will get unselected.
When I delete an item, the InstanceView shows nothing for the name and 0 for the id, as if its showing a "ghost?" instance, until you select a different one.
I've tried binding the selecting using the index of the selected Instance but that still has many of the same problems.
So I feel like I'm making some mistake in the way that I'm using NavigationView, and I was wondering what the best approach would be for creating a navigationView from an Array that works nicely across all devices.
Thanks!