uikit-interop

UIKit Interop

Review and write interop code for correct bridging between SwiftUI and UIKit in both directions.

Responsibility

Owns: UIViewRepresentable (makeUIView, updateUIView, Coordinator), UIViewControllerRepresentable (makeUIViewController, updateUIViewController), UIHostingController, UIHostingConfiguration (iOS 16+), context.animate {} for coordinated animations (iOS 17+), incremental adoption patterns.

Does NOT own: Pure SwiftUI views (swiftui-mastery skill), pure UIKit views (uikit-fundamentals skill), Core Animation bridging (core-animation skill).

Core Principles

1. UIViewRepresentable is a struct. makeUIView creates once, updateUIView syncs state. Never recreate the UIView in updateUIView.
2. Coordinator for delegates. Use the Coordinator class for UIKit delegate callbacks. The coordinator holds a reference to the parent representable via the binding, not a strong reference to the SwiftUI view.
3. context.animate {} for coordinated animations. On iOS 17+, use context.animate { } in updateUIView to coordinate UIKit animations with SwiftUI transitions.
4. UIHostingController for SwiftUI in UIKit. Embed SwiftUI views in UIKit via UIHostingController. Add as a child view controller — don't just add its view.
5. UIHostingConfiguration for cells. Use UIHostingConfiguration { SwiftUIView() } for collection/table view cells (iOS 16+). No need for a hosting controller per cell.
6. Incremental adoption. Start with leaf views (buttons, inputs) when adopting SwiftUI in a UIKit app. Start with UIKit wrappers for missing components when adopting UIKit in a SwiftUI app.
7. sizingOptions for hosting controllers. Set .intrinsicContentSize on UIHostingController to let Auto Layout size it correctly.

References

• references/uikit-interop-patterns.md — Representable protocols, hosting, coordinated animations, adoption patterns