HealthKit Code Review

Quick Reference

Review Checklist

• HKHealthStore.isHealthDataAvailable() called before any HealthKit operations
• Authorization requested only for needed data types (minimal permissions)
• requestAuthorization completion handler not misinterpreted as permission granted
• No attempt to determine read permission status (privacy by design)
• Query results dispatched to main thread for UI updates
• HKObjectQueryNoLimit used only with bounded predicates
• HKStatisticsQuery used for aggregations instead of manual summing
• Observer query completionHandler() always called (use defer)
• Background delivery registered in application(_:didFinishLaunchingWithOptions:)
• Background delivery entitlement added (iOS 15+)
• Correct units used for quantity types (e.g., count/min for heart rate)
• Long-running queries stored as properties and stopped in deinit

When to Load References

• Reviewing authorization/permissions flow -> authorization.md
• Reviewing HKSampleQuery, HKAnchoredObjectQuery, or predicates -> queries.md
• Reviewing HKObserverQuery or enableBackgroundDelivery -> background.md
• Reviewing HKQuantityType, HKCategoryType, or HKWorkout -> data-types.md

Review gates

Run in order. Do not state a finding in a later step until the pass condition for the current step is satisfied (each pass condition is answerable from the codebase under review).

1. Scope — Pass: Name the file path(s) and types/symbols using HealthKit, HKHealthStore, or HK* APIs (or state clearly that the diff touches none).
2. Availability and store — Pass: Cite the call site of isHealthDataAvailable() before HealthKit use, or document why omission is acceptable for the scoped code; cite where HKHealthStore is created or injected.
3. Authorization semantics — Pass: For each requestAuthorization / getRequestStatusForAuthorization, cite handler branches per references/authorization.md (e.g. success does not prove read access); do not infer read permission from authorizationStatus alone.
4. Queries and limits — Pass: For each query, cite predicate + limit (HKObjectQueryNoLimit only with a bounded predicate); for totals/aggregates, cite HKStatisticsQuery / collection vs manual summing per references/queries.md.
5. Observers and background — Pass: If HKObserverQuery or enableBackgroundDelivery appears, cite where the observer is started/stopped and where background delivery is registered; cite entitlements/Info.plist or flag missing config per references/background.md. If absent, Pass: one line “no observer/background in scope.”
6. Threading and lifecycle — Pass: Cite main-queue (or documented pattern) for UI updates from query callbacks; cite retention/stop()/deinit for long-running queries per checklist above.

Review Questions

1. Is isHealthDataAvailable() checked before creating HKHealthStore?
2. Does the code gracefully handle denied permissions (empty results)?
3. Are observer query completion handlers called in all code paths?
4. Is work in background handlers minimal (~15 second limit)?
5. Are HKQueryAnchors persisted per sample type (not shared)?