Queries

Query health and fitness data.

Overview

Use queries to read sample data from the HealthKit store. Queries can also be used to list all the sources for a particular type of data, or to do statistical calculations. For example, statistical queries can calculate the minimum and maximum heartrate for a given week, or the total step count for a given day.

You run a query by calling the HealthKit store’s execute(_:) method. A snapshot of the current results are asynchronously returned to the query’s results handler. Long-running queries continue to monitor the HealthKit store, and return any relevant changes to the query’s update handler. To return sorted or filtered results, give the query a sort descriptor or predicate.

Topics

First Steps

Reading Data from HealthKit

Use queries to request sample data from HealthKit.

Common Query Types

class HKSampleQuery

A general-purpose query that returns a snapshot of all the matching samples currently saved in the HealthKit store.

class HKQuantitySeriesSampleQuery

A query that accesses the series data associated with a quantity sample.

class HKAnchoredObjectQuery

A query that returns only recent changes to the HealthKit store, including a snapshot of new changes and continuous monitoring as a long-running query.

class HKObserverQuery

A long-running query that monitors the HealthKit store and updates your app when the HealthKit store saves or deletes a matching sample.

class HKCorrelationQuery

A query that performs complex searches based on the correlation’s contents, and returns a snapshot of all matching samples.

class HKDocumentQuery

A query that returns a snapshot of all matching documents currently saved in the HealthKit store.

class HKHeartbeatSeriesQuery

A query that returns the heartbeat data contained in a heartbeat series sample.

class HKQuery

An abstract class for all the query classes in HealthKit.

Sources and Devices

class HKSourceRevision

An object indicating the source of a HealthKit sample.

class HKSource

An object indicating the app or device that created a HealthKit sample

class HKDevice

A device that generates data for HealthKit.

class HKSourceQuery

A query that returns a list of sources (apps and devices) that have saved matching queries to the HealthKit store.

Calculating Statistics

class HKStatisticsQuery

A query that performs statistical calculations over a set of matching quantity samples, and returns the results.

class HKStatisticsCollectionQuery

A query that performs multiple statistics queries over a series of fixed-length time intervals, and returns the results.

class HKStatistics

An object that represents the result of calculating the minimum, maximum, average, or sum over a set of samples from the HealthKit store.

class HKStatisticsCollection

An object that manages a collection of statistics; each statistics object represents the data calculated over a separate time interval.

struct HKStatisticsOptions

Options for specifying the statistic to calculate.