swiftui-navigation

# SwiftUI Navigation

Navigation patterns for SwiftUI apps targeting iOS 26+ with Swift 6.3. Covers push navigation, multi-column layouts, sheet presentation, tab architecture, and deep linking. Patterns are backward-compatible to iOS 17 unless noted.

## Contents

- [NavigationStack (Push Navigation)](#navigationstack-push-navigation)
- [NavigationSplitView (Multi-Column)](#navigationsplitview-multi-column)
- [Sheet Presentation](#sheet-presentation)
- [Tab-Based Navigation](#tab-based-navigation)
- [Deep Links](#deep-links)
- [Common Mistakes](#common-mistakes)
- [Review Checklist](#review-checklist)
- [References](#references)

## NavigationStack (Push Navigation)

Use `NavigationStack` with a `NavigationPath` binding for programmatic, type-safe push navigation. Define routes as a `Hashable` enum and map them with `.navigationDestination(for:)`.

```swift
struct ContentView: View {
    @State private var path = NavigationPath()

    var body: some View {
        NavigationStack(path: $path) {
            List(items) { item in
                NavigationLink(value: item) {
                    ItemRow(item: item)
                }
            }
            .navigationDestination(for: Item.self) { item in
                DetailView(item: item)
            }
            .navigationTitle("Items")
        }
    }
}
```

**Programmatic navigation:**

```swift
path.append(item)        // Push
path.removeLast()        // Pop one
path = NavigationPath()  // Pop to root
```

**Router pattern:** For apps with complex navigation, use a router object that owns the path and sheet state. Each tab gets its own router instance injected via `.environment()`. Centralize destination mapping with a single `.navigationDestination(for:)` block or a shared `withAppRouter()` modifier.

See [references/navigationstack.md](references/navigationstack.md) for full router examples including per-tab stacks, centralized destination mapping, and generic tab routing.

## NavigationSplitView (Multi-Column)

Use `NavigationSplitView` for sidebar-detail layouts on iPad and Mac. Falls back to stack navigation on iPhone.

```swift
struct MasterDetailView: View {
    @State private var selectedItem: Item?

    var body: some View {
        NavigationSplitView {
            List(items, selection: $selectedItem) { item in
                NavigationLink(value: item) { ItemRow(item: item) }
            }
            .navigationTitle("Items")
        } detail: {
            if let item = selectedItem {
                ItemDetailView(item: item)
            } else {
                ContentUnavailableView("Select an Item", systemImage: "sidebar.leading")
            }
        }
    }
}
```

### Custom Split Column (Manual HStack)

For custom multi-column layouts (e.g., a dedicated notification column independent of selection), use a manual `HStack` split with `horizontalSizeClass` checks:

```swift
@MainActor
struct AppView: View {
  @Environment(\.horizontalSizeClass) private var horizontalSizeClass
  @AppStorage("showSecondaryColumn") private var showSecondaryColumn = true

  var body: some View {
    HStack(spacing: 0) {
      primaryColumn
      if shouldShowSecondaryColumn {
        Divider().edgesIgnoringSafeArea(.all)
        secondaryColumn
      }
    }
  }

  private var shouldShowSecondaryColumn: Bool {
    horizontalSizeClass == .regular
      && showSecondaryColumn
  }

  private var primaryColumn: some View {
    TabView { /* tabs */ }
  }

  private var secondaryColumn: some View {
    NotificationsTab()
      .environment(\.isSecondaryColumn, true)
      .frame(maxWidth: .secondaryColumnWidth)
  }
}
```

Use the manual HStack split when you need full control or a non-standard secondary column. Use `NavigationSplitView` when you want a standard system layout with minimal customization.

## Sheet Presentation

Prefer `.sheet(item:)` over `.sheet(isPresented:)` when state represents a selected model. Sheets should own their actions and call `dismiss()` internally.

```swift
@State private var selectedItem: Item?

.sheet(item: $selectedItem) { item in
    EditItemSheet(item: item)
}
```

**Presentation sizing (iOS 18+):** Control sheet dimensions with `.presentationSizing`:

```swift
.sheet(item: $selectedItem) { item in
    EditItemSheet(item: item)
        .presentationSizing(.form)  // .form, .page, .fitted, .automatic
}
```

`PresentationSizing` values:
- `.automatic` -- platform default
- `.page` -- roughly paper size, for informational content
- `.form` -- slightly narrower than page, for form-style UI
- `.fitted` -- sized by the content's ideal size

Fine-tuning: `.fitted(horizontal:vertical:)` constrains fitting axes; `.sticky(horizontal:vertical:)` grows but does not shrink in specified dimensions.

**Dismissal confirmation (macOS 15+ / iOS 26+):** Use `.dismissalConfirmationDialog("Discard?", shouldPresent: hasUnsavedChanges)` to prevent accidental dismissal of sheets with unsaved changes.

**Enum-driven sheet routing:** Define a `SheetDestination` enum that is `Identifiable`, store it on the router, and map it with a shared view modifier. This lets any child view present sheets without prop-drilling. See [references/sheets.md](references/sheets.md) for the full centralized sheet routing pattern.

## Tab-Based Navigation

Use the `Tab` API with a selection binding for scalable tab architecture. Each tab should wrap its content in an independent `NavigationStack`.

```swift
struct MainTabView: View {
    @State private var selectedTab: AppTab = .home

    var body: some View {
        TabView(selection: $selectedTab) {
            Tab("Home", systemImage: "house", value: .home) {
                NavigationStack { HomeView() }
            }
            Tab("Search", systemImage: "magnifyingglass", value: .search) {
                NavigationStack { SearchView() }
            }
            Tab("Profile", systemImage: "person", value: .profile) {
                NavigationStack { ProfileView() }
            }