Initializer

init(quantityType:quantitySamplePredicate:options:completionHandler:)

Initializes a statistics query instance that performs the specified calculations over the matching samples in the HeathKit store.

Declaration

init(quantityType: HKQuantityType, quantitySamplePredicate: NSPredicate?, options: HKStatisticsOptions = [], completionHandler handler: @escaping (HKStatisticsQuery, HKStatistics?, Error?) -> Void)

Parameters

quantityType

The type of sample to search for. This type must be an instance of the HKQuantityType class. You cannot perform statistics queries using other sample types.

quantitySamplePredicate

A predicate that limits the results returned by the query. You can pass nil if you want to perform the statistical calculation over all the samples of the specified type.

options

A list of options that define the type of statistical calculations performed and the way in which data from multiple sources are merged. For a list of valid options, see HKStatisticsOptions.

handler

A block that is called after the statistical calculations are complete. This block takes the following arguments:

query

A reference to the query calling this block.

results

A HealthKit statistics object that contains the requested statistical data, or nil if an error occurs.

error

If an error occurs, this parameter contains an object describing the error; otherwise, it is nil.

Return Value

A newly initialized statistics query object.

Discussion

After instantiating the query, call the HKHealthStore class’s executeQuery: method to run this query. Queries run on an anonymous background queue. As soon as the query is complete, the results handler is executed on the same background queue (but not necessarily on the same thread). You typically dispatch these results to the main queue to update the user interface.