uikit-app-modernization

UIKit App Modernization Patterns

Use this skill to make UIKit apps behave correctly in resizable, multi-window environments by removing legacy shared-state APIs. The full Apple-authored workflow, core principles, and task registry live in references/workflow.md; read it before editing.

When to Use

• Code references UIScreen.main / UIScreen.mainScreen
• Code reads interfaceOrientation for layout decisions
• App still uses application-lifecycle AppDelegate window setup and needs scene lifecycle
• Layout hard-codes insets or assumes symmetric safe areas
• User asks to prepare a UIKit app for multi-window or resizable scenes

When NOT to Use

• App is SwiftUI-only - use swiftui
• Task is general UIKit feature work with no deprecated shared-state API
• Task would require opportunistic cleanup of unrelated lines

Delivery Workflow

Use the checklist below and track progress:

UIKit modernization progress:
- [ ] Step 1: Detect target API occurrences across all in-scope files
- [ ] Step 2: Read the active task reference before editing
- [ ] Step 3: Apply the replacement for every occurrence (no TODO-only or empty diffs)
- [ ] Step 4: Verify every input file has a non-empty diff and control flow is preserved

Task Registry

Apply every task unless the request scopes to a subset. Each task has its own detection patterns, decision tree, and verification rules.

Task	Reference	Description
UIScreen.main modernization	references/uiscreen-task.md	Replace UIScreen.main with context-appropriate APIs
Orientation modernization	references/orientation-task.md	Replace layout-related orientation checks with size classes or window bounds
Scene lifecycle migration	references/scene-lifecycle-task.md	Migrate AppDelegate to SceneDelegate
Safe area insets	references/safe-area-task.md	Replace hard-coded insets and support asymmetric safe areas

Key rules (full list in references/workflow.md):

• Always apply a concrete replacement when the target API is present; a TODO-only or empty diff is a failure.
• Never replace dynamic values with literals or walk global state (UIApplication.shared, UIScreen.main).
• Never remove the old method when adding a new overload; keep it as a deprecated forwarder.
• Ask before risky signature or behavior changes; stay in scope with no opportunistic cleanup.