---
title: "apply(_:animatingDifferences:completion:)"
framework: appkit
role: symbol
role_heading: Instance Method
path: "appkit/nscollectionviewdiffabledatasource-axww/apply(_:animatingdifferences:completion:)"
---

# apply(_:animatingDifferences:completion:)

Updates the UI to reflect the state of the data in the specified snapshot, optionally animating the UI changes and executing a completion handler.

## Declaration

```swift
func apply(_ snapshot: NSDiffableDataSourceSnapshot<SectionIdentifierType, ItemIdentifierType>, animatingDifferences: Bool = true, completion: (() -> Void)? = nil)
```

## Parameters

- `snapshot`: The snapshot reflecting the new state of the data in the collection view.
- `animatingDifferences`: If doc://com.apple.documentation/documentation/Swift/true, the diffable data source computes the difference between the collection view’s current state and the new state in the snapshot, which is an O(n) operation, where n is the number of items in the snapshot. The differences in the UI between the current state and new state are animated. If doc://com.apple.documentation/documentation/Swift/false, the collection view UI is set to the new state without any animations, with no additional overhead for computing a diff. Any ongoing item animations are interrupted and the collection view’s content is reloaded immediately.
- `completion`: A closure to be executed when the animations are complete. This closure has no return value and takes no parameters. The system calls this closure from the main queue.

## Discussion

Discussion It’s safe to call this method from a background queue, but you must do so consistently in your app. Always call this method exclusively from the main queue or from a background queue.

## See Also

### Updating Data

- [snapshot()](appkit/nscollectionviewdiffabledatasource-axww/snapshot().md)