A sample that represents a quantity, including the value and the units.
- iOS 8.0+
- Mac Catalyst 13.0+
- watchOS 2.0+
A quantity sample contains one or more
HKQuantity objects. Each quantity represents a single piece of data with a single numeric value and the value’s associated units. For example, you can use quantity samples to record the user’s height, the user’s current heart rate, or the number of calories in a hamburger. HealthKit provides a wide range of quantity types, letting you track many different health and fitness features.
HKQuantity class is a subclass of the
HKSample class. Quantity samples are immutable; you set the sample’s properties when you create it, and they cannot change.
In iOS 13 and later and watchOS 6 and later,
HKQuantity is an abstract superclass for the
HKDiscrete concrete subclasses. The system automatically selects the correct subclass based on the
HKQuantity object used to create the sample.
Extend Quantity Samples
Like many HealthKit classes, you should not subclass the
HKQuantity class. You may extend this class by adding metadata with custom keys to save related data used by your app.
For more information, see