HKCorrelation class is a concrete subclass of the
HKObject class. HealthKit uses correlation types to create correlation objects that group multiple samples into a single data entry. iOS 8.0 provides support for using correlation types to represent both food and blood pressure.
- iOS 8.0+
- watchOS 2.0+
To create correlation type instances, use the
correlation convenience method and pass a valid correlation type identifier.
Like many HealthKit classes, correlation types are not extensible and should not be subclassed.
This class reuses the same instance whenever possible. Letting multiple queries share the same workout type helps reduce the overall memory usage.