BloodpressureQuery.swift

typealias HKSamplesResult = Result<[HKSample], Error>

func fetchAllBloodPressure(completion: @escaping (HKSamplesResult) -> ()) {
        let correlationType = HKCorrelationType.correlationType(forIdentifier: .bloodPressure)!
        let query = HKCorrelationQuery(type: correlationType, predicate: nil, samplePredicates: nil) {
            (query, results, error) in
            guard let correlations = results, error == nil else {
                print("Error during the query: \(String(describing: error?.localizedDescription))")
                completion(.failure(HKStoreManagerError.QueryExecutionError))
                return
            }
            completion(.success(correlations))
        }
        healthStore.execute(query)
    }