example.swift

class Store: ObservableObject {
    @Published var id: String? = nil
    
    init() {
        id = UserDefaults.standard.string(forKey: "key")
        
        let _ = $id.sink {
            UserDefaults.standard.set(id, forKey: "key")
        }
    }
}

class Example: View {
    @ObservedObject var store = Store()
    
    var body: some View {
        NavigationView {
            NavigationLink(destination: Text(id ?? ""), tag: "test", selection: $store.id) {
                Text("Press me")
            }
        }
    }
}