Hello, community and Apple engineers. I need your help.
Our app has the following issue: NavigationStack pushes a view twice if the NavigationStack is inside TabView and NavigationStack uses a navigation path of custom Hashable elements.
Our app works with issues in Xcode 18 Beta 13 + iOS 18.0. The same issue happened on previous beta versions of Xcode 18.
The issue isn’t represented in iOS 17.x and everything worked well before iOS 18.0 beta releases.
I was able to represent the same issue in a clear project with two simple views. I will paste the code below.
Several notes:
We use a centralised routing system in our app where all possible routes for navigation path are implemented in a View extension called withAppRouter().
We have a enum RouterDestination that contains all possible routes and is resolved in withAppRouter() extension.
We use Router class that contains @Published var path: [RouterDestination] = [] and this @Published property is bound to NavigationStack. In the real app, we need to have an access to this path property for programmatic navigation purposes.
Our app uses @ObservableObject / @StateObject approach.
import SwiftUI
struct ContentView: View {
@StateObject private var router = Router()
var body: some View {
TabView {
NavigationStack(path: $router.path) {
NavigationLink(value: RouterDestination.next, label: {
Label("Next", systemImage: "plus.circle.fill")
})
.withAppRouter()
}
}
}
}
enum RouterDestination: Hashable {
case next
}
struct SecondView: View {
var body: some View {
Text("Screen 2")
}
}
class Router: ObservableObject {
@Published var path: [RouterDestination] = []
}
extension View {
func withAppRouter() -> some View {
navigationDestination(for: RouterDestination.self) { destination in
switch destination {
case .next:
return SecondView()
}
}
}
}
Below you can see the GIF with the issue:
What I tried to do:
Use iOS 17+ @Observable approach. It didn’t help.
Using @State var path: [RouterDestination] = [] directly inside View seems to help. But it is not what we want as we need this property to be @Published and located inside Router class where we can get an access to it, and use for programmatic navigation if needed.
I ask Apple engineers to help with that, please, and if it is a bug of iOS 18 beta, then please fix it in the next versions of iOS 18.0
ulian_onua
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Our app has an architecture based on ViewModels.
Currently, we are working on migrating from the ObservableObject protocol to the Observable macro (iOS 17+).
The official docs about this are available here: https://developer.apple.com/documentation/swiftui/migrating-from-the-observable-object-protocol-to-the-observable-macro
Our ViewModels that were previously annotated with @StateObject now use just @State, as recommended in the official docs.
Some of our screens (a screen is a SwiftUI view with a corresponding ViewModel) are presented modally. We expect that after dismissing a SwiftUI view that was presented modally, its corresponding ViewModel, which is owned by this view (via the @State modifier), will be deinitialized. However, it seems there is a memory leak, as the ViewModel is not deinitialized after a modal view is dismissed.
Here's a simple code where ModalView is presented modally (through the .sheet modifier), and ModalViewModel, which is a @State of ModalView, is never deinitialized.
import SwiftUI
import Observation
@Observable
final class ModalViewModel {
init() {
print("Simple ViewModel Inited")
}
deinit {
print("Simple ViewModel Deinited") // never called
}
}
struct ModalView: View {
@State var viewModel: ModalViewModel = ModalViewModel()
let closeButtonClosure: () -> Void
var body: some View {
ZStack {
Color.yellow
.ignoresSafeArea()
Button("Close") {
closeButtonClosure()
}
}
}
}
struct ContentView: View {
@State var presentSheet: Bool = false
var body: some View {
Button("Present sheet modally") {
self.presentSheet = true
}
.sheet(isPresented: $presentSheet) {
ModalView {
self.presentSheet = false
}
}
}
}
#Preview {
ContentView()
}
Is this a bug in the iOS 17 beta version or intended behavior? Is it possible to build a relationship between the View and ViewModel in a way where the ViewModel will be deinitialized after the View is dismissed?
Thank you in advance for the help.