ContentView.swift

func readTotalStepCount() {
        guard let stepCountType = HKObjectType.quantityType(forIdentifier: .stepCount) else {
            fatalError("*** Unable to get the step count type ***")
        }
        
        let query = HKStatisticsQuery.init(quantityType: stepCountType,
                                           quantitySamplePredicate: get24hPredicate(),
                                           options: [HKStatisticsOptions.cumulativeSum, HKStatisticsOptions.separateBySource]) { (query, results, error) in
            let totalStepCount = results?.sumQuantity()!.doubleValue(for: HKUnit.count())
            print("Total step count: \(totalStepCount ?? 0)")
            if ((results?.sources) != nil){
                for source in (results?.sources)! {
                    let separateSourceStepCount = results?.sumQuantity(for: source)!.doubleValue(for: HKUnit.count())
                    print("Seperate Source total step count: \(separateSourceStepCount ?? 0)")
                }
            }
        }
        
        healthStore.execute(query)
    }