// create store object
let healthStore = HKHealthStore()

// create HKWorkoutSession with ActivityType (Cycling, Walking ...)
let workoutSession = HKWorkoutSession(activityType: HKWorkoutActivityType.CrossTraining, locationType: HKWorkoutSessionLocationType.Indoor)
let heartRateUnit = HKUnit(fromString: "count/min")
var anchor = HKQueryAnchor(fromValue: Int(HKAnchoredObjectQueryNoAnchor))

workoutSession.delegate = self

/// Indicates whether HealthKit is available on this device
guard HKHealthStore.isHealthDataAvailable() == true else {
    infoLabel.setText("not available")
    return
}
/// To create samples that store a numerical value
guard let quantityType = HKQuantityType.quantityTypeForIdentifier(HKQuantityTypeIdentifierHeartRate) else {
    //..
    return
}
/// Request permission to save and read the specified data types
let dataTypes = Set(arrayLiteral: quantityType)
healthStore.requestAuthorizationToShareTypes(nil, readTypes: dataTypes) { (success, error) -> Void in
    if success == false {
        //..
    }
}

extension WKInterfaceController : HKWorkoutSessionDelegate {

func workoutSession(workoutSession: HKWorkoutSession, didChangeToState toState: HKWorkoutSessionState, fromState: HKWorkoutSessionState, date: NSDate) {
    dispatch_async(dispatch_get_main_queue()) {
        switch toState {
            case .Running:
                self.workoutDidStart(date)
            case .Ended:
                self.workoutDidEnd(date)
            default:
                print("unexpected \(toState)")
        }
    }
}

func workoutSession(workoutSession: HKWorkoutSession, didFailWithError error: NSError) {
    print("workOutSession Error : \(error.localizedDescription)")
    }
}