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# HKCumulativeQuantitySample

A sample that represents a cumulative quantity.

```
class HKCumulativeQuantitySample
```

## Overview

A quantity sample contains one or more [`HKQuantity`](/documentation/HealthKit/HKQuantity) objects. Each quantity represents a single piece of data with a single numeric value and the value’s associated units. Use these samples to store data that accumulates over time, such as step count, active energy burned, or walking distance.

The [`HKCumulativeQuantitySample`](/documentation/HealthKit/HKCumulativeQuantitySample) class is a concrete subclass of the [`HKQuantitySample`](/documentation/HealthKit/HKQuantitySample) class. Cumulative quantity samples are immutable; you set the sample’s properties when you create it, and they cannot change.

### Extend Cumulative Quantity Samples

Like many HealthKit classes, you should not subclass the [`HKCumulativeQuantitySample`](/documentation/HealthKit/HKCumulativeQuantitySample) class. You may extend this class by adding metadata with custom keys to save related data used by your app.

For more information, see [`init(type:quantity:start:end:metadata:)`](/documentation/HealthKit/HKQuantitySample/init(type:quantity:start:end:metadata:)).

## Topics

### Accessing Calculated Data

[`sumQuantity`](/documentation/HealthKit/HKCumulativeQuantitySample/sumQuantity)

The sum of all the quantities contained by the sample.


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