A type that identifies samples that group multiple subsamples.
- iOS 8.0+
- watchOS 2.0+
Use correlation types to:
Request permission to read or write matching quantity samples.
Create and share matching quantity samples.
Query for matching quantity samples.
HealthKit provides two correlation types: blood pressure and food.
Using Correlation Types
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.