heartRateFullExample.swift

public func subscribeToHeartBeatChanges() {

  // Creating the sample for the heart rate
  guard let sampleType: HKSampleType =
    HKObjectType.quantityType(forIdentifier: .heartRate) else {
      return
  }

  /// Creating an observer, so updates are received whenever HealthKit’s
  // heart rate data changes.
  self.heartRateQuery = HKObserverQuery.init(
    sampleType: sampleType,
    predicate: nil) { [weak self] _, _, error in
      guard error == nil else {
        log.warn(error!)
        return
      }

      /// When the completion is called, an other query is executed
      /// to fetch the latest heart rate
      self.fetchLatestHeartRateSample(completion: { sample in
        guard let sample = sample else {
          return
        }

        /// The completion in called on a background thread, but we
        /// need to update the UI on the main.
        DispatchQueue.main.async {

          /// Converting the heart rate to bpm
          let heartRateUnit = HKUnit(from: "count/min")
          let heartRate = sample
            .quantity
            .doubleValue(for: heartRateUnit)

          /// Updating the UI with the retrieved value
          self?.heartRateLabel.setText("\(Int(heartRate))")
        }
      })
  }
}

public func fetchLatestHeartRateSample(
  completion: @escaping (_ sample: HKQuantitySample?) -> Void) {

  /// Create sample type for the heart rate
  guard let sampleType = HKObjectType
    .quantityType(forIdentifier: .heartRate) else {
      completion(nil)
    return
  }

  /// Predicate for specifiying start and end dates for the query
  let predicate = HKQuery
    .predicateForSamples(
      withStart: Date.distantPast,
      end: Date(),
      options: .strictEndDate)

  /// Set sorting by date.
  let sortDescriptor = NSSortDescriptor(
    key: HKSampleSortIdentifierStartDate,
    ascending: false)

  /// Create the query
  let query = HKSampleQuery(
    sampleType: sampleType,
    predicate: predicate,
    limit: Int(HKObjectQueryNoLimit),
    sortDescriptors: [sortDescriptor]) { (_, results, error) in

      guard error == nil else {
        print("Error: \(error!.localizedDescription)")
        return
      }
      
      completion(results?[0] as? HKQuantitySample)
  }

  self.healthStore.execute(query)
}

Could you please provide some additional context? Where does this code go, and what includes are required? Thanks!

Hello, this is an example that belongs to the medium article in here: https://medium.com/ios-os-x-development/apple-watch-app-displaying-the-heart-rate-b3555f3e148d

Please upload complete example with all variable defined inti

Hey @nabeelawan00, this is not an open source project. I am happy to support you, just reach out to contact@blackmirror.media.