UIKit Modernization

Guidance for the scene-based life cycle and resizability changes that UIKit requires in the iOS 27 cycle — the highest-impact UIKit change in years, because it gates whether your app launches at all.

When to Use

Use this skill when:

• Building against the iOS 27 SDK and your app uses only a UIApplicationDelegate (no scene delegate)
• Your app "won't launch" after updating to the latest SDK
• Making an iPhone app adapt to arbitrary window sizes (iPhone Mirroring on Mac, iPhone apps on iPad)
• Replacing UIScreen.main, interface idiom, or orientation checks with adaptive equivalents
• Adopting iOS 27 additive APIs — tab bar sidebar/prominent tab, nav bar minimization, menu image visibility, CoreMotion/CoreLocation Body protocols
• Planning a UIKit → scene-lifecycle migration

Example Prompts

• "My UIKit app won't launch on iOS 27"
• "How do I adopt the scene-based life cycle?"
• "What replaces UIScreen.main?"
• "How do I make my iPhone app resizable?"
• "Should I use the interface idiom or size classes for layout?"
• "How do I put a tab bar in a sidebar on iPhone? (iOS 27)"
• "What's the View Annotations API for Siri?"

What This Skill Provides

• The scene-lifecycle requirement at iOS 27 (apps without a UISceneDelegate no longer launch) and the migration path
• A don't/do table for replacing UIScreen.main, screen.scale, screen.bounds, idiom, and orientation with scene/trait/size-class equivalents
• The new iOS 27 additive APIs — prominentTabIdentifier, UITabBarControllerSidebar.preferredPlacement, barMinimizationSafeAreaAdjustment, UIMenuElement.preferredImageVisibility, deviceMotionBody/headingBody
• Apple Intelligence touchpoints (menu "Ask Siri", View Annotations, drag-and-drop resource loading)
• How to let Xcode 27's app-modernization agent do the mechanical rewrites

Related

• UIKit-SwiftUI Bridging – embedding SwiftUI in a modernized scene-based UIKit app
• App Composition – app-level integration and UIKit → SwiftUI migration priority
• SwiftUI Layout – size-class-driven adaptive layout, the recommended replacement for idiom/orientation checks