---
title: "startWatchApp(with:completion:)"
framework: healthkit
role: symbol
role_heading: Instance Method
path: "healthkit/hkhealthstore/startwatchapp(with:completion:)"
---

# startWatchApp(with:completion:)

Launches or wakes the companion watchOS app to create a new workout session.

## Declaration

```swift
func startWatchApp(with workoutConfiguration: HKWorkoutConfiguration, completion: @escaping @Sendable (Bool, (any Error)?) -> Void)
```

```swift
func startWatchApp(toHandle workoutConfiguration: HKWorkoutConfiguration) async throws
```

## Parameters

- `workoutConfiguration`: The configuration data for a new workout session on the watch.
- `completion`: A block that this method calls after launching the Watch app. The system calls this block, passing the following parameters:

## Discussion

Discussion Use this method to launch the companion watchOS app on a paired Apple Watch. After launching, the system calls the handle method on the watchOS app’s delegate and passes the provided workout configuration. Use the workout configuration to start a new workout session on the watch. To launch a mirrored workout from the iOS companion app, call this method in the iOS companion. let configuration = HKWorkoutConfiguration() configuration.activityType = .running configuration.locationType = .outdoor

do {     try await store.startWatchApp(toHandle: configuration) } catch {     // Handle the error here.     fatalError("*** An error occurred while starting a workout on Apple Watch: \(error.localizedDescription) ***") }

logger.debug("*** Workout Session Started ***") Next, set up the mirrored workout in the WKApplicationDelegate object’s handle(_:) method. class AppDelegate: NSObject, WKApplicationDelegate {

func handle(_ workoutConfiguration: HKWorkoutConfiguration) {         Task {             await WorkoutManager.shared.startWorkout()             logger.debug("Successfully started workout")         }     } }

extension WorkoutManager {     func startWorkout() async {

let configuration = HKWorkoutConfiguration()         configuration.activityType = .running         configuration.locationType = .outdoor

let session: HKWorkoutSession         do {             session = try HKWorkoutSession(healthStore: store,                                            configuration: configuration)         } catch {             // Handle failure here.             fatalError("*** An error occurred: \(error.localizedDescription) ***")         }

let builder = session.associatedWorkoutBuilder()

let source = HKLiveWorkoutDataSource(healthStore: store,                                              workoutConfiguration: configuration)

source.enableCollection(for: HKQuantityType(.stepCount), predicate: nil)         builder.dataSource = source

session.delegate = self         builder.delegate = self

self.session = session         self.builder = builder

let start = Date()

// Start the mirrored session on the companion iPhone.         do {             try await session.startMirroringToCompanionDevice()         }         catch {             fatalError("*** Unable to start the mirrored workout: \(error.localizedDescription) ***")         }

// Start the workout session.         session.startActivity(with: start)

do {             try await builder.beginCollection(at: start)         } catch {             // Handle the error here.             fatalError("*** An error occurred while starting the workout: \(error.localizedDescription) ***")         }

logger.debug("*** Workout Session Started ***")     } }

## See Also

### Managing workout sessions

- [workoutSessionMirroringStartHandler](healthkit/hkhealthstore/workoutsessionmirroringstarthandler.md)
- [pause(_:)](healthkit/hkhealthstore/pause(_:).md)
- [resumeWorkoutSession(_:)](healthkit/hkhealthstore/resumeworkoutsession(_:).md)