HKCorrelation class is a concrete subclass of the
HKSample class. Use a correlation object to group multiple samples into a single data entry. HealthKit uses correlations to represent both blood pressure and food. Blood pressure correlations always include two quantity samples that represent the systolic and diastolic values. In contrast, food correlations can contain a wide range of dietary information about the food, including information about the fat, protein, carbohydrates, energy, and vitamins consumed.
- iOS 8.0+
- watchOS 2.0+
Correlations are immutable: You set the correlation’s properties when the object is first created, and they cannot change.
Like many HealthKit classes, the
HKCorrelation class should not be subclassed. You can extend the correlation class by adding metadata with custom keys as appropriate for your app. For more information, see the