What’s new in HealthKit

Sleep analysis

• Introducing sleep stages

• Apple Watch will automatically track all the different sleep stages you go through when you’re asleep

• this data will be accessible from the Health app and saved in HealthKit

• apps can read/write sleep analysis data via HKCategoryTypeIdentifier.sleepAnalysis

• three sleep stages: REM, core, deep

public enum HKCategoryValueSleepAnalysis: Int {
  case inBed
  case asleep // ❌ removed
  case asleepUnspecified // 👈🏻 Replaces asleep, used when user is asleep but no sleep stage is specified
  case awake
  case asleepCore // 👈🏻 New
  case asleepDeep // 👈🏻 New
  case asleepREM  // 👈🏻 New
}

• new predicate HKCategoryValuePredicateProviding to access HealthKit samples, for example:

let stagePredicate = HKCategoryValueSleepAnalysis.predicateForSamples(.equalTo, value: .asleepREM)
let queryPredicate = HKSamplePredicate.sample(type: HKCategoryType(.sleepAnalysis), predicate: stagePredicate)
let sleepQuery = HKSampleQueryDescriptor(predicates: [queryPredicate], sortDescriptors: [])

// Run the query
let sleepSamples = try async sleepQuery.result(for: healthStore) // 👈🏻 available since iOS 15.4

Swift async

• available since iOS 15.4

• see types that conform to the new HKAsyncQuery to see which queries support swift concurrency

Workouts

• new workouts API in iOS 16 and watchOS 9 to make it possible to capture mixed activities workouts like triathlon

• each activity is represented via one HKWorkoutActivity

• each HKWorkoutActivity comes with

  • its own HKWorkoutConfiguration, which includes its activity type

  • an array of HKWorkoutEvent

• you can read statistics for each HKWorkoutActivity separately

• workout activities are not required to be contiguous

• between activities you can create a HKWorkoutActivity with type HKWorkoutActivityType.transition

• all activities will be put together under the same HKWorkout object

• new predicates for querying only a specific type of activity within workouts, e.g., predicateForWorkoutActivities(operatorType:quantityType:averageQuantity:)

Heart rate recovery

• new Cardio Recovery data type HKQuantityTypeIdentifier.heartRateRecoveryOneMinute

• additional context can be added as metadata

Vision prescriptions

• from iOS 16, we can save glasses and contacts prescriptions in HealthKit

• HKObjectType.visionPrescriptionType()

  • optionally we can store digital copy of the physical prescription

• new HKVisionPrescription class, along with HKGlassesLensSpecification and HKGlassesPrescription specification objects