<!--
{
  "availability" : [
    "iOS: 13.0.0 -",
    "iPadOS: 13.0.0 -",
    "macCatalyst: 13.0.0 -",
    "macOS: 10.15.0 -",
    "tvOS: 13.0.0 -",
    "visionOS: 1.0.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "PhotoKit",
  "identifier" : "/documentation/Photos/PHPhotoLibraryAvailabilityObserver",
  "metadataVersion" : "0.1.0",
  "role" : "Protocol",
  "symbol" : {
    "kind" : "Protocol",
    "modules" : [
      "Photos"
    ],
    "preciseIdentifier" : "c:objc(pl)PHPhotoLibraryAvailabilityObserver"
  },
  "title" : "PHPhotoLibraryAvailabilityObserver"
}
-->

# PHPhotoLibraryAvailabilityObserver

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

```
protocol PHPhotoLibraryAvailabilityObserver : NSObjectProtocol
```

## 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:`](/documentation/Photos/PHPhotoLibraryAvailabilityObserver/photoLibraryDidBecomeUnavailable(_:))

Tells the observer that the photo library’s availability changed.

## Relationships

### Inherits From

[`NSObjectProtocol`](/documentation/ObjectiveC/NSObjectProtocol)

---

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