Visual overview

Use the workflow to follow the task, and the architecture map to separate responsibilities. These are conceptual maps; the guide below defines implementation details and verification limits.

01 / WorkflowFrom intent to a checked result
  1. Own state outside the layout
  2. Choose split or overlay
  3. Adapt axes and proportions
  4. Verify state and accessibility
02 / ArchitectureResponsibility boundaries
  1. Boundary 1Primary and secondary content
  2. Boundary 2Arrangement style and environment
  3. Boundary 3SDK availability and fallback

Connected responsibilities, not a required class hierarchy or an execution trace.

Context

Apple symbol metadata checked 2026-09-21 lists iOS/iPadOS 27.1 beta, not 27.0, for ArrangementView and UIArrangementViewController. A runtime guard cannot make an older SDK recognize these symbols.

Pattern

In SwiftUI, ArrangementView owns primary and secondary view content. arrangementViewStyle(_:) selects a split or overlay presentation. Restrict layout axes through the style’s axes(_:), and use splitArrangementLayoutRatio(...) for proportional constraints. A custom ArrangementViewStyle implements makeBody(configuration:) using the supplied primary/secondary content. Keep app state outside layout decisions so changing orientation or arrangement preserves selection, drafts and ongoing work.

In UIKit, use setViewController(_:for:animated:) with primary/secondary placements and updateArrangement(_:animated:) to change between UISplitArrangement and UIOverlayArrangement. Custom arrangements implement the documented Arrangement contract, including default and per-placement view properties. Query placement and state through the controller, rather than inferring them from child ordering.

Review split, overlay, narrow/wide sizes, accessibility text sizes and state preservation independently. For older deployment targets, provide a supported layout fallback. Compile both paths using an SDK that declares the new APIs.

Sources: SwiftUI September updates, UIKit September updates.

The same update pages describe reserved-region queries, hinge updates, vertical bar placement and camera-capture scene accessories. Retrieve their specific symbol metadata before adoption; do not assume every item shares the same minimum OS. Prefer documented reserved-region geometry over hardcoded hinge dimensions.

Anti-Patterns

  • Do not require migration from a working NavigationSplitView or custom layout.
  • Do not confuse .split or .axes on an unrelated type with an arrangement API.
  • Do not claim an iPad resize test validates Duo folding or outer-display behavior.

Verification

analyze_swift_project recognizes nine specific arrangement API references with source links and 27.1 metadata, excluding comments, strings and same-file type shadows. This is lexical recognition, not Swift name resolution or a missing-guard diagnostic. Tests validate recognition; real arrangement builds/runtime behavior remain unverified because the local SDK is older.