UIKit & Bridging

You MUST use this skill for ANY UIKit bridging, Auto Layout, Combine, TextKit, or UIKit animation work.

Quick Reference

Symptom / Task	Reference
UIViewRepresentable, UIViewControllerRepresentable	See skills/uikit-bridging.md
Embedding SwiftUI in UIKit (UIHostingController)	See skills/uikit-bridging.md
Coordinator pattern, updateUIView lifecycle	See skills/uikit-bridging.md
"Unable to simultaneously satisfy constraints"	See skills/auto-layout-debugging.md
Constraint conflicts, ambiguous layout	See skills/auto-layout-debugging.md
Views not appearing, positioned incorrectly	See skills/auto-layout-debugging.md
CAAnimation completion handler not firing	See skills/uikit-animation-debugging.md
Spring physics wrong on device, duration mismatch	See skills/uikit-animation-debugging.md
Animation jank, CATransaction timing	See skills/uikit-animation-debugging.md
Combine publishers, AnyCancellable lifecycle	See skills/combine-patterns.md
@Published properties, Combine ↔ async/await	See skills/combine-patterns.md
When to use Combine vs async/await	See skills/combine-patterns.md
TextKit 2 architecture, NSTextLayoutManager	See skills/textkit-ref.md
Writing Tools integration (iOS 26)	See skills/textkit-ref.md
SwiftUI TextEditor, TextKit 1 migration	See skills/textkit-ref.md

Decision Tree

digraph uikit {
    start [label="UIKit task" shape=ellipse];
    what [label="What do you need?" shape=diamond];

    start -> what;
    what -> "skills/uikit-bridging.md" [label="wrap UIKit in SwiftUI\nor SwiftUI in UIKit"];
    what -> "skills/auto-layout-debugging.md" [label="constraint errors,\nlayout issues"];
    what -> "skills/uikit-animation-debugging.md" [label="CAAnimation bugs,\nspring physics,\ncompletion handlers"];
    what -> "skills/combine-patterns.md" [label="publishers, sinks,\n@Published,\nasync/await bridge"];
    what -> "skills/textkit-ref.md" [label="text layout,\nWriting Tools,\nTextKit migration"];
}

1. UIViewRepresentable / UIViewControllerRepresentable / UIHostingController? → skills/uikit-bridging.md
2. "Unable to simultaneously satisfy constraints" / layout bugs? → skills/auto-layout-debugging.md
3. CAAnimation completion missing / spring physics wrong / animation jank? → skills/uikit-animation-debugging.md
4. Combine publishers / AnyCancellable / @Published / Combine ↔ async bridge? → skills/combine-patterns.md
5. TextKit 2 / Writing Tools / TextEditor / TextKit 1 migration? → skills/textkit-ref.md
6. Pure SwiftUI view question (no UIKit bridging)? → /skill axiom-swiftui
7. Design decisions, HIG, Liquid Glass, SF Symbols, typography? → /skill axiom-design
8. Block retain cycles in UIKit callbacks? → See axiom-performance (skills/objc-block-retain-cycles.md)
9. Memory leaks from Combine subscriptions? → Start with skills/combine-patterns.md, then axiom-performance if leak persists

Conflict Resolution

uikit vs swiftui: When working with UI code:

• Use uikit when wrapping UIKit in SwiftUI or vice versa, or debugging UIKit-specific issues (Auto Layout, CAAnimation)
• Use swiftui for pure SwiftUI views, navigation, layout, animations

uikit vs concurrency: When Combine interacts with async/await:

• Use uikit (skills/combine-patterns.md) for bridging Combine pipelines with async/await
• Use concurrency for pure async/await patterns, actors, Sendable

uikit vs performance: When animations or layout cause performance issues:

1. Try uikit FIRST — Most animation jank is CATransaction timing or layer state, not a profiling issue
2. Only use performance if animation logic is correct but rendering is slow

uikit vs axiom-data: When @Published properties relate to data persistence:

• Use uikit for Combine publisher patterns and @Published lifecycle
• Use axiom-data for SwiftData/Core Data model layer concerns

Anti-Rationalization

Thought	Reality
"I'll just use UIHostingController, it's simple"	Hosting has sizing, lifecycle, and navigation edge cases. skills/uikit-bridging.md covers the gotchas.
"Auto Layout error is just a warning, I'll ignore it"	Unsatisfied constraints cause unpredictable layout at runtime. Fix them now.
"I know how CAAnimation works"	90% of CAAnimation bugs are CATransaction timing, not Core Animation. Check skills/uikit-animation-debugging.md.
"Combine is dead, just rewrite with async/await"	Combine has no deprecation notice. Rewriting working pipelines wastes time. skills/combine-patterns.md covers when to migrate vs maintain.
"TextKit 1 still works fine"	TextKit 1 misses Writing Tools integration and has known layout bugs Apple won't fix. See skills/textkit-ref.md.
"I'll store cancellables in a local variable"	Local AnyCancellable deallocates immediately, killing the subscription.

Example Invocations

User: "How do I wrap a UIKit view in SwiftUI?" → Read: skills/uikit-bridging.md

User: "I'm getting 'Unable to simultaneously satisfy constraints'" → Read: skills/auto-layout-debugging.md

User: "My CAAnimation completion handler never fires" → Read: skills/uikit-animation-debugging.md

User: "Should I use Combine or async/await for this?" → Read: skills/combine-patterns.md

User: "How do I integrate Writing Tools with my text editor?" → Read: skills/textkit-ref.md

User: "My SwiftUI view has a memory leak from a Combine subscription" → Read: skills/combine-patterns.md

User: "How do I embed SwiftUI in my UIKit app?" → Read: skills/uikit-bridging.md