# HKQuantitySeriesSampleQueryDescriptor A query interface that reads the series data associated with quantity samples using Swift concurrency. ``` struct HKQuantitySeriesSampleQueryDescriptor ``` ## Overview Use [`HKQuantitySeriesSampleQueryDescriptor`](/documentation/HealthKit/HKQuantitySeriesSampleQueryDescriptor) to read the series data included in quantity samples. Apps can save any quantity data as a series using the [`HKQuantitySeriesSampleBuilder`](/documentation/HealthKit/HKQuantitySeriesSampleBuilder) class; however, series data typically comes from high-frequency data saved during a workout. Any [`HKQuantitySample`](/documentation/HealthKit/HKQuantitySample) that has a [`count`](/documentation/HealthKit/HKQuantitySample/count) greater than `1` contains series data. > Important: > Only use this query when you need direct access to the high-frequency series data, for example when visualizing the raw data or when exporting objects from the HealthKit store. For most common calculations, consider using a statistical query instead. Statistical queries correctly handle quantity data, whether the samples represent a single quantity or a series. To read the individual data entries, create a predicate that identifies the sample type and limits the results to the desired data. For example, to read the series for a particular sample object, include a [`predicateForObject(with:)`](/documentation/HealthKit/HKQuery/predicateForObject(with:)) predicate. However, if you’re reading high-frequency data during a workout, you may want to include a [`predicateForSamples(withStart:end:options:)`](/documentation/HealthKit/HKQuery/predicateForSamples(withStart:end:options:)) predicate that returns matching series data based on the workout’s time period instead. ```swift // Create the predicate for the data. let heartRate = HKQuantityType(.heartRate) let objectPredicate = HKQuery.predicateForObject(with: myHeartRateSample.uuid) let predicate = HKSamplePredicate.quantitySample(type: heartRate, predicate: objectPredicate) // Create the source descriptor. let seriesDescriptor = HKQuantitySeriesSampleQueryDescriptor(predicate: predicate, options: .orderByQuantitySampleStartDate) // Get the AsyncSequence that returns the individual data entries. let series = seriesDescriptor.results(for: store) // Access each data entry in the series for try await entry in series { // Process results here. let steps = entry.quantity.doubleValue(for: .count()) print(steps) } ``` While this method returns an , unlike the long-running queries, this sequence has a finite size. Iterating over the sequence asynchronously returns data entries, automatically terminating after you receive all the data. ## Topics ### Creating Series Query Descriptors [`init(predicate: HKSamplePredicate, options: HKQuantitySeriesSampleQueryDescriptor.Options)`](/documentation/HealthKit/HKQuantitySeriesSampleQueryDescriptor/init(predicate:options:)) Creates a quantity series query descriptor. [`struct Options`](/documentation/HealthKit/HKQuantitySeriesSampleQueryDescriptor/Options-swift.struct) Options used when querying series data. ### Running Queries [`func results(for: HKHealthStore) -> HKQuantitySeriesSampleQueryDescriptor.Results`](/documentation/HealthKit/HKQuantitySeriesSampleQueryDescriptor/results(for:)) Runs a one-shot query that returns an asynchronous sequence of matching series samples. [`struct Results`](/documentation/HealthKit/HKQuantitySeriesSampleQueryDescriptor/Results) An asynchronous sequence that emits data from the quantity series query. [`struct Result`](/documentation/HealthKit/HKQuantitySeriesSampleQueryDescriptor/Result) A set of results from a quantity series sample descriptor. ### Accessing Query Properties [`var options: HKQuantitySeriesSampleQueryDescriptor.Options`](/documentation/HealthKit/HKQuantitySeriesSampleQueryDescriptor/options-swift.property) A set of options for the query. For a list of possible values, see [`HKQuantitySeriesSampleQueryDescriptor.Options`](/documentation/HealthKit/HKQuantitySeriesSampleQueryDescriptor/Options-swift.struct). [`var predicate: HKSamplePredicate`](/documentation/HealthKit/HKQuantitySeriesSampleQueryDescriptor/predicate) A predicate that defines the set of series samples that the query returns. ### Default Implementations [HKAsyncSequenceQuery Implementations](/documentation/HealthKit/HKQuantitySeriesSampleQueryDescriptor/HKAsyncSequenceQuery-Implementations) ## Relationships ### Conforms To [`HKAsyncSequenceQuery`](/documentation/HealthKit/HKAsyncSequenceQuery) [`Copyable`](/documentation/Swift/Copyable) [`Escapable`](/documentation/Swift/Escapable) --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)