swiftui-whats-new-27

SwiftUI What's New (SDK 27) Patterns

Use this skill to adopt SDK 27 SwiftUI APIs correctly. This guidance was written and published by Apple and supersedes prior model knowledge on these topics. Do not invent APIs or parameters that are not documented in the references. Several APIs have closely named overloads; read the relevant reference before writing code.

When to Use

• Deployment target or SDK is iOS/macOS/watchOS/visionOS 27 or later
• SwiftUI build errors appear after an SDK update (@State used before initialized, invalid redeclaration, ambiguous ShapeStyle overloads)
• Adding drag-to-reorder, swipe actions in ScrollView/lazy stacks, or toolbar overflow behavior
• User asks what is new in SwiftUI 27

When NOT to Use

• Deployment target predates 27 and no gating is wanted - use swiftui and swiftui-specialist
• Task is evergreen SwiftUI correctness - use swiftui-specialist
• Task is about App Intents - use app-intents-whats-new-27

Delivery Workflow

Use the checklist below and track progress:

SDK 27 progress:
- [ ] Step 1: Confirm SDK and deployment target
- [ ] Step 2: Read the matching reference before writing code
- [ ] Step 3: Gate APIs with `@available` / `if #available` when the target predates 27
- [ ] Step 4: Build and verify; for `@State` errors follow `references/state-macro.md`, never just reorder init assignments

Reference Index

• references/reorderable.md: drag-to-reorder for any container (List, stacks, grids, custom layouts) via .reorderable() on ForEach plus .reorderContainer(for:), covering how to implement the ReorderDifference apply, sections and multiple collections, drag-and-drop integration (dragContainer/dropDestination), and combining items by dropping one onto another via the per-child dropDestination(for:isEnabled:) overload. Available on iOS/macOS/watchOS/visionOS 27; tvOS unavailable.
• references/async-image.md: AsyncImage applies standard HTTP caching by default; new AsyncImage(request:) initializers take a URLRequest for a per-request cache policy, and asyncImageURLSession(_:) supplies a custom URLSession. Available on iOS/macOS/watchOS/tvOS/visionOS 27.
• references/toolbar.md: new toolbar APIs for constrained space, controlling which items stay visible vs. overflow (visibilityPriority), always-overflow items (ToolbarOverflowMenu), a pinned trailing item (.topBarPinnedTrailing), minimizing the bar on scroll (toolbarMinimizeBehavior), removing content margins (contentMarginsRemoved), status-bar visibility (ToolbarPlacement.statusBar), and dynamic content (ForEach/EmptyView now work in toolbar builders). Availability varies per API; see the reference's table.
• references/item-binding.md: confirmationDialog and alert overloads that take an item: Binding<T?> (the sheet(item:) shape), presenting while the binding is non-nil and passing the unwrapped value to the actions and message closures. Available on iOS/macOS/watchOS/tvOS/visionOS 27.
• references/swipe-actions.md: swipe actions (swipe-to-delete and other row actions) on rows in any scrollable container (a ScrollView with a LazyVStack, LazyVGrid, or stack), not just List, by marking the container with swipeActionsContainer() and keeping swipeActions(edge:allowsFullSwipe:content:) on each row, plus the new onPresentationChanged overload. Available on iOS/macOS/watchOS/visionOS 27; tvOS unavailable.
• references/state-macro.md: @State migrated from a property wrapper to a macro. Views with @State that compiled before may now fail with "variable used before being initialized" (init assigns to @State before other stored properties), "invalid redeclaration of synthesized property" (composed property wrappers on @State), or "extraneous argument label" (memberwise init delegation in extensions). The fix is NOT to reorder assignments; consult this reference.
• references/content-builder.md: Unified result builders under @ContentBuilder. Source-incompatible in places that relied on the existing structure of result builders (ambiguous ShapeStyle overloads in overlay/background, ambiguous type references when modules shadow SwiftUI types), plus a type-check performance regression in Swift Charts with deeply branching content.