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# HKCorrelationTypeIdentifier

The identifiers that create correlation type objects.

```
struct HKCorrelationTypeIdentifier
```

## Overview

To create an [`HKCorrelationType`](/documentation/HealthKit/HKCorrelationType) instance, pass an [`HKCorrelationTypeIdentifier`](/documentation/HealthKit/HKCorrelationTypeIdentifier) value to the [`correlationType(forIdentifier:)`](/documentation/HealthKit/HKObjectType/correlationType(forIdentifier:)) method.

## Topics

### Correlation Types

[`bloodPressure`](/documentation/HealthKit/HKCorrelationTypeIdentifier/bloodPressure)

A correlation sample that combines a systolic sample and a diastolic sample into a single blood pressure reading.

[`food`](/documentation/HealthKit/HKCorrelationTypeIdentifier/food)

Food correlation types combine any number of nutritional samples into a single food object.

### Initializers

[`init(rawValue:)`](/documentation/HealthKit/HKCorrelationTypeIdentifier/init(rawValue:))

Returns a newly initialized correlation type identifier using the provided string.


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