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# HKSampleType

An abstract superclass for all classes that identify a specific type of sample when working with the HealthKit store.

```
class HKSampleType
```

## Overview

The [`HKSampleType`](/documentation/HealthKit/HKSampleType) class is an abstract subclass of the [`HKObjectType`](/documentation/HealthKit/HKObjectType) class, used to represent data samples. Never instantiate an [`HKSampleType`](/documentation/HealthKit/HKSampleType) object directly. Instead, work with one of its concrete subclasses: [`HKCategoryType`](/documentation/HealthKit/HKCategoryType), [`HKCorrelationType`](/documentation/HealthKit/HKCorrelationType), [`HKQuantityType`](/documentation/HealthKit/HKQuantityType), or [`HKWorkoutType`](/documentation/HealthKit/HKWorkoutType) classes.

## Topics

### Checking the Duration Restriction

[`isMinimumDurationRestricted`](/documentation/HealthKit/HKSampleType/isMinimumDurationRestricted)

A Boolean value that indicates whether samples of this type have a minimum time interval between the start and end dates.

[`minimumAllowedDuration`](/documentation/HealthKit/HKSampleType/minimumAllowedDuration)

The minimum duration if the sample type has a restricted duration.

[`isMaximumDurationRestricted`](/documentation/HealthKit/HKSampleType/isMaximumDurationRestricted)

A Boolean value that indicates whether samples of this type have a maximum time interval between the start and end dates.

[`maximumAllowedDuration`](/documentation/HealthKit/HKSampleType/maximumAllowedDuration)

The maximum duration if the sample type has a restricted duration.

### Checking on Recalibrating Estimates

[`allowsRecalibrationForEstimates`](/documentation/HealthKit/HKSampleType/allowsRecalibrationForEstimates)

A Boolean value that indicates whether HealthKit supports recalibrating the prediction algorithm used to produce estimates for this sample type.


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