swiftui-uikit-interop

SwiftUI-UIKit Interop

Bridge UIKit and SwiftUI in both directions: wrap UIKit views and controllers for use in SwiftUI, embed SwiftUI views into existing UIKit view hierarchies, and coordinate state updates safely. Targets Swift 6.3 / iOS 26+.

Bridging Directions
Representable Lifecycle and Coordinator
State Synchronization and Feedback Loops
Embedding SwiftUI in UIKit
Route by Task
Common Mistakes
Review Checklist
References

Bridging Directions

UIKit into SwiftUI:
- UIViewRepresentable: Wraps a custom UIView (e.g., text views, maps, custom controls).
- UIViewControllerRepresentable: Wraps a UIViewController (e.g., camera controllers, document pickers, share sheets).
SwiftUI into UIKit:
- UIHostingController: Embeds SwiftUI views into UIKit view controller hierarchies.
- UIHostingConfiguration: Embeds SwiftUI views directly into UICollectionView and UITableView cells (iOS 16+).

Representable Lifecycle and Coordinator

makeCoordinator() ──> makeUIView(context:) ──> updateUIView(uiView, context:) ──> dismantleUIView(uiView, coordinator:)

makeCoordinator(): Called once to create the delegate/coordinator object.
makeUIView(context:): Called once to instantiate the UIKit view and assign delegates.
updateUIView(_:context:): Called on every SwiftUI state change affecting the view. Must be idempotent.
dismantleUIView(_:coordinator:): Cleanup point when the view leaves the hierarchy. Invalidate timers, unregister observers.

State Synchronization and Feedback Loops

[!WARNING] Prevent infinite update cycles: When UIKit notifies the coordinator of a change (e.g., textViewDidChange), the coordinator updates SwiftUI state via @Binding. This triggers updateUIView. Always check for value equality before applying updates to the UIKit view:
if uiView.text != text { uiView.text = text }

Embedding SwiftUI in UIKit

When adding a UIHostingController as a child view controller:

addChild(hostingController)
view.addSubview(hostingController.view)
Set Auto Layout constraints
hostingController.didMove(toParent: self)

Use UIHostingConfiguration for modern cell layouts in UICollectionView/UITableView without manual controller management.

Route by Task

For wrapping MKMapView, UITextView, and camera capture controllers, read Map, Text, and Camera Wrappers.
For PHPickerViewController, MFMailComposeViewController, UIActivityViewController, and search controllers, read Picker, Mail, Share, and Search Wrappers.
For PDFView, QLPreviewController, and MFMessageComposeViewController, read PDF and Message Wrappers.
For embedding SwiftUI in UIKit table/collection cells, navigation transitions, and full hosting migration, read Hosting Migration.

Common Mistakes

Re-creating heavy UIKit objects inside updateUIView instead of configuring the existing instance.
Omitting equality checks in updateUIView, triggering continuous render feedback loops.
Adding a UIHostingController's view without calling addChild and didMove(toParent:).
Forgetting to clean up delegates, KVO, or NotificationCenter observers in dismantleUIView.
Ignoring safe area insets and sizing calculations (sizeThatFits) in custom representables.

Review Checklist

makeCoordinator used for delegates, target-actions, and data sources
updateUIView guards against redundant assignments to avoid feedback loops
Child view controller containment calls (addChild, didMove) properly paired
Cell layouts in UIKit use UIHostingConfiguration where available
Subscribed observers and display links invalidated in dismantleUIView
Auto Layout constraints configured with translatesAutoresizingMaskIntoConstraints = false

About this skill

Contents