Compose Multiplatform ↔ SwiftUI

Compose Multiplatform produces a UIViewController (via ComposeUIViewController). SwiftUI
consumes it through UIViewControllerRepresentable. This skill covers both directions.

Compose Multiplatform iOS support is stable as of version 1.8.0 (May 2025).

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Official Documentation

Topic	Link
Compose Multiplatform ↔ SwiftUI	https://kotlinlang.org/docs/multiplatform/compose-swiftui-integration.html
Compose Multiplatform ↔ UIKit	https://kotlinlang.org/docs/multiplatform/compose-uikit-integration.html
UIViewControllerRepresentable	https://developer.apple.com/documentation/swiftui/uiviewcontrollerrepresentable
makeCoordinator()	https://developer.apple.com/documentation/swiftui/uiviewcontrollerrepresentable/makecoordinator()-9vwm8
Compose Multiplatform examples (interop)	https://github.com/JetBrains/compose-multiplatform/tree/master/examples/interop

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Quick Pattern Reference

Need	Pattern
Embed Compose in SwiftUI (stateless)	ComposeUIViewController + minimal UIViewControllerRepresentable
Embed Compose in SwiftUI (bidirectional state)	makeCoordinator() — coordinator holds the UIViewController
Embed SwiftUI inside Compose	UIKitViewController factory with a wrapping UIViewController
Embed UIKit inside Compose	UIKitView / UIKitViewController
Pass SwiftUI state → Compose	updateUIViewController calls context.coordinator.update*(…)
Pass Compose events → SwiftUI	Callback closures provided at ComposeUIViewController creation

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Anti-Patterns

• ❌ .id(someState) on a Compose view — tears down and recreates the UIViewController on every change; causes visual glitches and wasted memory
• ❌ Calling buildController: closure inside updateUIViewController — creates a new Compose lifecycle on every SwiftUI update
• ❌ Storing a @State copy of the Kotlin holder — use makeCoordinator() for a stable single reference
• ❌ Passing KMP types into feature modules — wrap in Swift types before the feature boundary (see swift-kmp skill)

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Reference Router

Reference	Load when
references/compose-in-swiftui.md	Embedding Compose in SwiftUI; UIViewControllerRepresentable wiring; ComposeUIViewController Kotlin setup
references/swiftui-in-compose.md	Embedding SwiftUI/UIKit inside Compose; UIKitViewController; UIKitView
references/state-sharing.md	Bidirectional state: makeCoordinator() pattern; Kotlin mutableStateOf bridge; StateFlow → AsyncStream

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Review Checklist

• Stateless Compose view uses simple UIViewControllerRepresentable with empty updateUIViewController
• Stateful/bidirectional view uses makeCoordinator() — Kotlin controller created once per lifetime
• .id() trick is not used to force Compose state updates
• SwiftUI state flows into Compose via context.coordinator.update*(…) in updateUIViewController
• Compose-to-SwiftUI callbacks are provided at build time in the makeCoordinator() / build closure
• Info.plist contains CADisableMinimumFrameDurationOnPhone = YES (required for Compose on iOS)
• UIKit views embedded in Compose use UIKitView (view) or UIKitViewController (controller)
• interactionMode is set correctly for Compose views that need native touch passthrough

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Info.plist Requirement

Compose Multiplatform on iOS requires one Info.plist entry or the app crashes at runtime:

<key>CADisableMinimumFrameDurationOnPhone</key>
<true/>

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See Also

• For KMP-specific bridge architecture (interactors, type mapping, flow bridging) → swift-kmp skill
• For Kotlin ComposeUIViewController setup in KMP shared code → references/compose-in-swiftui.md