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# ARSessionObserver

Methods you can implement to respond to changes in the state of an AR session.

```
protocol ARSessionObserver : NSObjectProtocol
```

## Overview

This protocol defines optional methods common to the [`ARSessionDelegate`](/documentation/ARKit/ARSessionDelegate), [`ARSCNViewDelegate`](/documentation/ARKit/ARSCNViewDelegate), and [`ARSKViewDelegate`](/documentation/ARKit/ARSKViewDelegate) protocols. You can implement this protocol’s methods when adopting one of those protocols.

## Topics

### Responding to Tracking Quality Changes

[`session(_:cameraDidChangeTrackingState:)`](/documentation/ARKit/ARSessionObserver/session(_:cameraDidChangeTrackingState:))

Informs the delegate of changes to the quality of ARKit’s device position tracking.

[`session(_:didChange:)`](/documentation/ARKit/ARSessionObserver/session(_:didChange:))

Listen and react to geo-tracking state changes.

### Handling Interruptions

[`sessionWasInterrupted(_:)`](/documentation/ARKit/ARSessionObserver/sessionWasInterrupted(_:))

Tells the delegate that the session has temporarily stopped processing frames and tracking device position.

[`sessionInterruptionEnded(_:)`](/documentation/ARKit/ARSessionObserver/sessionInterruptionEnded(_:))

Tells the delegate that the session has resumed processing frames and tracking device position.

[`sessionShouldAttemptRelocalization(_:)`](/documentation/ARKit/ARSessionObserver/sessionShouldAttemptRelocalization(_:))

Asks the delegate whether to attempt recovery of world-tracking state after an interruption.

### Receiving Audio Data

[`session(_:didOutputAudioSampleBuffer:)`](/documentation/ARKit/ARSessionObserver/session(_:didOutputAudioSampleBuffer:))

Tells the delegate that a new sample buffer of recorded audio is available.

### Handling Errors

[`session(_:didFailWithError:)`](/documentation/ARKit/ARSessionObserver/session(_:didFailWithError:))

Tells the delegate that the session has stopped running due to an error.

[`ARErrorDomain`](/documentation/ARKit/ARErrorDomain)

The domain for error objects produced by an AR session.

### Managing Collaboration

[`session(_:didOutputCollaborationData:)`](/documentation/ARKit/ARSessionObserver/session(_:didOutputCollaborationData:))

Provides information for nearby users about your perspective in the environment.


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