State Restoration Skill for Claude

Glob: **/*StateRestoration*.swift, **/*AppState*.swift, **/*SceneStorage*.swift
Grep: "SceneStorage" or "NavigationPath" or "selectedTab" or "scrollPosition"

Grep: "NavigationStack" or "NavigationSplitView" or "TabView" or "NavigationLink"

StateRestoration/
├── AppState.swift                  # Codable state model
├── StateRestorationManager.swift   # Auto-save/restore orchestrator
├── NavigationStateModifier.swift   # Navigation path persistence (optional)
├── ScrollRestorationModifier.swift # Scroll position persistence (optional)
├── TabRestorationModifier.swift    # Tab selection persistence (optional)
└── FormDraftManager.swift          # Form draft auto-save (optional)

@main
struct MyApp: App {
    @State private var stateManager = StateRestorationManager()

    var body: some Scene {
        WindowGroup {
            ContentView()
                .environment(stateManager)
        }
    }
}

struct ContentView: View {
    @Environment(StateRestorationManager.self) private var stateManager

    var body: some View {
        @Bindable var sm = stateManager
        NavigationStack(path: $sm.navigationPath) {
            HomeView()
                .navigationDestination(for: Route.self) { route in
                    RouteView(route: route)
                }
        }
        .modifier(NavigationStateModifier(stateManager: stateManager))
    }
}

struct MainTabView: View {
    @Environment(StateRestorationManager.self) private var stateManager

    var body: some View {
        @Bindable var sm = stateManager
        TabView(selection: $sm.selectedTab) {
            HomeTab().tag(0)
            SearchTab().tag(1)
            ProfileTab().tag(2)
        }
        .modifier(TabRestorationModifier(stateManager: stateManager))
    }
}

struct ItemListView: View {
    let items: [Item]

    var body: some View {
        ScrollView {
            LazyVStack {
                ForEach(items) { item in
                    ItemRow(item: item)
                }
            }
        }
        .modifier(ScrollRestorationModifier(scrollViewID: "item-list"))
    }
}

struct ComposeView: View {
    @State private var draftManager = FormDraftManager(formID: "compose")
    @State private var title = ""
    @State private var body = ""

    var body: some View {
        Form {
            TextField("Title", text: $title)
            TextEditor(text: $body)
        }
        .onAppear { draftManager.restore(into: &title, &body, keys: "title", "body") }
        .onChange(of: title) { draftManager.save(key: "title", value: title) }
        .onChange(of: body) { draftManager.save(key: "body", value: body) }
        .onSubmit { draftManager.clearDraft() }
    }
}

@Test
func stateRestoredFromDisk() async throws {
    let manager = StateRestorationManager(storage: .file(directory: tempDir))
    manager.selectedTab = 2
    manager.saveState()

    let restored = StateRestorationManager(storage: .file(directory: tempDir))
    restored.restoreState()
    #expect(restored.selectedTab == 2)
}

@Test
func timeLimitedRestoreExpires() async throws {
    let manager = StateRestorationManager(
        storage: .file(directory: tempDir),
        restoreBehavior: .timeLimited(minutes: 30)
    )
    // Simulate state saved 60 minutes ago
    manager.appState.lastSavedDate = Date().addingTimeInterval(-3600)
    manager.saveState()

    let restored = StateRestorationManager(
        storage: .file(directory: tempDir),
        restoreBehavior: .timeLimited(minutes: 30)
    )
    restored.restoreState()
    #expect(restored.selectedTab == 0) // Default, not restored
}

@Test
func formDraftClearedOnSubmit() async throws {
    let draft = FormDraftManager(formID: "test", storage: .file(directory: tempDir))
    draft.save(key: "title", value: "My Draft")
    #expect(draft.value(for: "title") == "My Draft")

    draft.clearDraft()
    #expect(draft.value(for: "title") == nil)
}

enum Route: Codable, Hashable {
    case detail(id: UUID)
    case settings
    case profile(userID: String)
}

// NavigationPath supports Codable serialization
let representation = navigationPath.codable
let data = try JSONEncoder().encode(representation)

// Use String tags instead of Int for readability and stability
TabView(selection: $stateManager.selectedTab) {
    HomeView().tag("home")
    SearchView().tag("search")
    ProfileView().tag("profile")
}

// Save draft only after user pauses typing (1 second)
.onChange(of: textContent) {
    draftManager.save(key: "content", value: textContent)
    // Internally debounced — won't write to disk on every keystroke
}