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# HKWorkoutSessionDelegate

The session delegate protocol that defines an interface for receiving notifications about errors and changes in the workout session’s state.

```
protocol HKWorkoutSessionDelegate : NSObjectProtocol
```

## Overview

All the methods are required. HealthKit calls these methods on an anonymous serial background queue.

## Topics

### Tracking workout sessions

[`workoutSession(_:didChangeTo:from:date:)`](/documentation/HealthKit/HKWorkoutSessionDelegate/workoutSession(_:didChangeTo:from:date:))

Tells the delegate that the session’s state changed.

[`workoutSession(_:didFailWithError:)`](/documentation/HealthKit/HKWorkoutSessionDelegate/workoutSession(_:didFailWithError:))

Tells the delegate that the session failed with an error.

[`workoutSession(_:didGenerate:)`](/documentation/HealthKit/HKWorkoutSessionDelegate/workoutSession(_:didGenerate:))

Tells the delegate that the system generated a workout event.

[`workoutSession(_:didBeginActivityWith:date:)`](/documentation/HealthKit/HKWorkoutSessionDelegate/workoutSession(_:didBeginActivityWith:date:))

Tells the delegate that a new workout session began.

[`workoutSession(_:didEndActivityWith:date:)`](/documentation/HealthKit/HKWorkoutSessionDelegate/workoutSession(_:didEndActivityWith:date:))

Tells the session that the current workout activity ended.

### Working with mirrored sessions

[`workoutSession(_:didDisconnectFromRemoteDeviceWithError:)`](/documentation/HealthKit/HKWorkoutSessionDelegate/workoutSession(_:didDisconnectFromRemoteDeviceWithError:))

Tells the delegate that the mirrored workout session disconnected from the primary session.

[`workoutSession(_:didReceiveDataFromRemoteWorkoutSession:)`](/documentation/HealthKit/HKWorkoutSessionDelegate/workoutSession(_:didReceiveDataFromRemoteWorkoutSession:))

Passes data from the remote workout session to the session delegate.


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