code for http://learningswift.brightdigit.com/wwdc-2018-and-healthkit-fitness-apps-introducing-hkliveworkoutbuilder

querying-changes-watchOS4.swift

  func startWorkoutWithHealthStore(_ healthStore: HKHealthStore, 
                                   andActivityType activityType: HKWorkoutActivityType, 
                                   withSampleTypes sampleTypes: [HKSampleType]) -> HKWorkoutSession {
    let configuration = HKWorkoutConfiguration()
    configuration.activityType = activityType
    
    let session : HKWorkoutSession
    do {
      session = try HKWorkoutSession(configuration: configuration)
    } catch let error {
      // let the user know about the error
      return
    }
    let queries = sampleTypes.map{
      HKObserverQuery(sampleType: $0, predicate: nil, updateHandler: self.observerQuery)
    }
    for query in queries {
      healthStore.execute(query)
    }
    healthStore.start(session)
    self.session = session
    self.healthStore = healthStore
    return session  
  }
  
  func observerQuery(_ query: HKObserverQuery, 
                     hasCompleted completed: HKObserverQueryCompletionHandler, 
                     withError error: Error?) {
    guard let healthStore = self.healthStore else {
      #warning("Throw Error Message to User if no healthStore available")
      return
    }
    guard let sampleType = query.objectType as? HKSampleType else {
      completed()
      return
    }
    // only query for the latest value
    let sort = [
      NSSortDescriptor(key: HKSampleSortIdentifierStartDate, ascending: false)
    ]
    let sampleQuery = HKSampleQuery(sampleType: sampleType, predicate: nil, limit: 1, sortDescriptors: sort, resultsHandler: self.sampleQuery)
    
    healthStore.execute(sampleQuery)
    
  }
  
  func sampleQuery(_ query: HKSampleQuery, 
                   withSamples samples: [HKSample]?, 
                   andError error: Error?) {
    guard let quantityType = query.objectType as? HKQuantityType else {
      return
    }
    
    if let error = error {
      #warning("Theres an error with the query")
      return
    }
    
    guard let sample = samples?.first as? HKQuantitySample else {
      #warning("Theres no sample with the query.")
      return
    }
    
    DispatchQueue.main.async {
      // update the UI here
    }
  }  

querying-changes-watchOS5.swift

  func workoutBuilder(_ workoutBuilder: HKLiveWorkoutBuilder, 
    didCollectDataOf collectedTypes: Set<HKSampleType>) {
    
    for sampleType in collectedTypes {
      if let quantityType = sampleType as? HKQuantityType {
        guard let statistic = workoutBuilder.statistics(for: quantityType) else {
          continue
        }
        guard let quantity = statistic.mostRecentQuantity() else {
          continue
        }
        DispatchQueue.main.async {
          // update the UI based on the most recent quantitiy
        }
      } else {
        // handle other HKSampleType subclasses
      }
    }
  }

starting-a-workout-watchOS4.swift

func startWorkoutWithHealthStore(_ healthStore: HKHealthStore, 
                                 andActivityType activityType: HKWorkoutActivityType
                                ) -> HKWorkoutSession {
  let configuration = HKWorkoutConfiguration()
  configuration.activityType = activityType
  
  let session : HKWorkoutSession
  do {
    session = try HKWorkoutSession(configuration: configuration)
  } catch let error {
    // let the user know about the error
    return
  }
  
  healthStore.start(session)
  self.session = session
  self.healthStore = healthStore
  return session  
}

starting-a-workout-watchOS5.swift

  func startWorkoutWithHealthStore(_ healthStore: HKHealthStore, andActivityType activityType: HKWorkoutActivityType, withSampleTypes sampleTypes: [HKSampleType]) -> HKWorkoutSession {
    let configuration = HKWorkoutConfiguration()
    configuration.activityType = activityType
    
    let session : HKWorkoutSession
    do {
      session = try HKWorkoutSession(healthStore: healthStore, configuration: configuration)
    } catch let error {
      // let the user know about the error
      return
    }

    let builder = session.associatedWorkoutBuilder()
    builder.delegate = self
    builder.dataSource = HKLiveWorkoutDataSource(healthStore: healthStore, workoutConfiguration: configuration) 
    session.delegate = self

    self.builder = builder
    self.session = session
    self.healthStore = healthStore

    session.startActivity()

    builder.beginCollection(withStart: Date()) { (success, error) in
      // do something when the data collection begins
    }

    return session  
  }

workout-state-change-update-ui.swift

  func workoutSession(_ workoutSession: HKWorkoutSession, 
    didChangeTo toState: HKWorkoutSessionState, 
    from fromState: HKWorkoutSessionState, 
    date: Date) {

    DispatchQueue.main.async {
      // based on the change update the UI on the main thread
    }
  }