Specify the kind of data used in HealthKit.
HKObject subclasses to identify the different types of data stored in HealthKit:
HKCharacteristicrepresents data that does not typically change over time (for example, blood type).
HKQuantityrepresents samples that contain a numeric value (for example calories consumed).
HKCategoryrepresents samples that contain an option from a short list of possible values (for example sleep analysis).
HKCorrelationrepresents complex samples that contain a number of quantity or category samples (for example, a food sample that includes a number of nutrition samples).
HKWorkoutrepresents a workout and its associated data (for more information, see Workouts).
To create a type object, call the appropriate
HKObject class method, and pass in the desired type identifier.
You can use the resulting object types to request permission to access the data, to save new data to the HealthKit store, or to read data from the HealthKit store.