NavigationLink deinit ObservedObject after background task is done - swiftui

Question

I have a problem with deallocating SecondVM each time when I push to new View from my ContentView and ContentVM finishes his work.
Description
After pushing to Second View, the ObservableObject is deallocated after task in ContentVM is done.
My example code bellow ContentView and `ContentVM:
final class ContentVM: ObservableObject {
#Published var title = "Start"
init() {
DispatchQueue.main.asyncAfter(deadline: .now() + 5) {
self.title = "Changed"
}
}
}
struct ContentView: View {
#ObservedObject var vm = ContentVM()
var body: some View {
NavigationView {
VStack {
NavigationLink(destination: Second()) {
Text("Go To second")
}
Spacer()
.frame(height: 40)
Text(vm.title)
}
}
}
}
and Second and SecondVM
final class SecondVM: ObservableObject {
#Published var name: String = ""
func getName() {
DispatchQueue.main.asyncAfter(deadline: .now() + 2) {
self.name = "TEST"
}
}
}
struct Second: View {
#ObservedObject var vm = SecondVM()
var body: some View {
Text(vm.name)
.padding(50)
.background(vm.name.isEmpty ? Color.white : Color.black)
.foregroundColor(Color.white)
.onAppear {
self.vm.getName()
}
}
}
As you can see on the video bellow problem appears only, when I push to Second View. The Black rectangle appears correctly and after task from ContentVM is done then, this black rectangle disappears because of deallocating SecondVM. How to avoid this kind of behaviour?

Answer 1

Here is solution - make link destination equatable, so when ContentView updated on own state change it does not recreate destination view (which otherwise is what happens and is origin of observed issue).
Tested with Xcode 11.5b2
// in ContentView, id can be any type but constant in this case
NavigationLink(destination: Second(id: 1).equatable()) {
Text("Go To second")
}
// SecondView
struct Second: View, Equatable {
let id: Int
static func == (lhs: Second, rhs: Second) -> Bool {
lhs.id == rhs.id
}
#ObservedObject var vm = SecondVM()
// .. other code