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# photoLibraryDidChange(_:)

Tells your observer that a set of changes has occurred in the Photos library.

```
func photoLibraryDidChange(_ changeInstance: PHChange)
```

## Parameters

`changeInstance`

An object representing the changes.

## Discussion

Use the provided [`PHChange`](/documentation/Photos/PHChange) object to find out which, if any, of the albums or collections you’re interested in have changed and get detailed change information. Call the change object’s [`changeDetailsForObject:`](/documentation/Photos/PHChange/changeDetailsForObject:) method to get information about changes to an asset’s contents or metadata properties or about a collection’s metadata properties. Call the change object’s [`changeDetails(for:)`](/documentation/Photos/PHChange/changeDetails(for:)-33a6n) to get information about changes to a collection’s list of members (or to any other fetch result).

Photos calls this method on an arbitrary queue. If you need to update your app’s UI as a result of the change, dispatch to the main queue.

---

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