MapKit

Build map-based and location-aware features targeting iOS 17+ with SwiftUI MapKit and modern CoreLocation async APIs. Use Map with MapContentBuilder for views, CLLocationUpdate.liveUpdates() for streaming location, and CLMonitor for geofencing.

Read references/mapkit-patterns.md when you need full map setup, search, routes, Look Around, snapshots, or iOS 26 place APIs. Read references/mapkit-corelocation-patterns.md when the task involves location update lifecycle, geofencing, background location, testing, or privacy keys.

Workflow

1. Define the exact map/location capability and request only the authorization it needs.
2. Choose SwiftUI Map or UIKit hosting, then establish camera ownership, selection, annotations, and overlay identity.
3. Keep search, geocoding, directions, and live-location tasks cancellable and scoped to the current query/session.
4. Handle denied/restricted/reduced-accuracy states and avoid treating coordinates as always available.
5. Verify empty results, movement, camera changes, route failures, localization, offline/network transitions, and background rules.

Route by Task

• Read core implementation details for SwiftUI maps, camera, annotations, overlays, live updates, authorization, geocoding, search, and directions.
• Read MapKit patterns for clustering, Look Around, snapshots, complex routes, and full map setup.
• Read Core Location patterns for CLLocationUpdate, monitoring, service sessions, background behavior, and testing.

Core Decisions

• Do not infer authorization from API availability or a non-nil cached location.
• Use stable identities for annotations and overlays.
• Debounce and cancel search/geocoding work when input changes.
• Treat size, viewport, and user interaction as live state rather than fixed screen assumptions.

Common Mistakes

DON'T: Request always authorization upfront. DO: Start with when-in-use authorization. On iOS 18+, hold a CLServiceSession for the feature lifetime; request .always only for background features that need system relaunch after termination.

DON'T: Use CLLocationManagerDelegate for simple location fetches on iOS 17+. DO: Use CLLocationUpdate.liveUpdates() async stream for cleaner, more concise code.

DON'T: Ignore CLLocationUpdate diagnostics such as denied, globally denied, or unavailable location. DO: Stop or degrade the feature, show recovery UI such as Settings guidance, and keep search/manual flows usable.

DON'T: Let liveUpdates() run from an unowned task after the map/view is gone. DO: Store the Task, cancel it when the feature stops, and filter invalid, inaccurate, stale, or impossible movement fixes.

DON'T: Force-unwrap CLPlacemark properties — they are all optional. DO: Use nil-coalescing: placemark.locality ?? "Unknown".

DON'T: Fire MKLocalSearchCompleter queries on every keystroke. DO: Debounce with .task(id: searchText) + Task.sleep(for: .milliseconds(300)).

DON'T: Silently fail when location authorization is denied. DO: Detect .denied status and show an alert with a Settings deep link.

DON'T: Assume geocoding always succeeds — handle empty results and network errors.

Review Checklist

• Info.plist has NSLocationWhenInUseUsageDescription with specific reason
• Authorization denial handled with Settings deep link
• CLLocationUpdate task cancelled when not needed (battery)
• Location accuracy appropriate for the use case
• Map annotations use Identifiable data with stable IDs
• Geocoding errors handled (network failure, no results)
• Search completer input debounced
• CLMonitor limited to 20 conditions, instance kept alive
• Background location uses CLBackgroundActivitySession
• Map tested with VoiceOver
• Map annotation view models and location UI updates are @MainActor-isolated

References

• references/mapkit-patterns.md — Map setup, annotations, search, routes, clustering, Look Around, snapshots.
• references/mapkit-corelocation-patterns.md — CLLocationUpdate, CLMonitor, CLServiceSession, background location, testing.
• Core implementation details -- setup, API wiring, and focused implementation recipes moved out of the entrypoint.