---
title: PHPhotoLibraryAvailabilityObserver
framework: photos
role: symbol
role_heading: Protocol
path: photos/phphotolibraryavailabilityobserver
---

# PHPhotoLibraryAvailabilityObserver

A protocol to adopt to have the system notify your app when the availability of a photo library changes.

## Declaration

```swift
protocol PHPhotoLibraryAvailabilityObserver : NSObjectProtocol
```

## Overview

Overview Observing changes to the photo library’s availability is primarily of concern with Mac apps created using macOS and Mac Catalyst, where the library may reside on an external drive or in cloud storage.

## Topics

### Observing Availability Changes

- [photoLibraryDidBecomeUnavailable(_:)](photos/phphotolibraryavailabilityobserver/photolibrarydidbecomeunavailable(_:).md)

## Relationships

### Inherits From

- [NSObjectProtocol](objectivec/nsobjectprotocol.md)

## See Also

### Observing Library Availability

- [register(_:)](photos/phphotolibrary/register(_:)-gm0a.md)
- [unregisterAvailabilityObserver(_:)](photos/phphotolibrary/unregisteravailabilityobserver(_:).md)
- [unavailabilityReason](photos/phphotolibrary/unavailabilityreason.md)