The HKCharacteristicType class is a concrete subclass of the HKObjectType class. HealthKit uses characteristic types to represent data that does not typically change over time. Unlike the other object types, characteristic types cannot be used to create new HealthKit objects. Instead, users must enter and edit their characteristic data using the Health app. Characteristic types are used only when asking for permission to read data from the HealthKit store.


HealthKit provides three characteristic types: biological sex, blood type and birthdate. To create characteristic type instances, use the characteristicType(forIdentifier:) convenience method.


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