---
title: "willTransition(from:to:)"
framework: appkit
role: symbol
role_heading: Instance Method
path: "appkit/nscollectionviewelement/willtransition(from:to:)"
---

# willTransition(from:to:)

Tells the element that the layout object of the collection view is about to change.

## Declaration

```swift
@MainActor optional func willTransition(from oldLayout: NSCollectionViewLayout, to newLayout: NSCollectionViewLayout)
```

## Parameters

- `oldLayout`: The current layout object used by the collection view.
- `newLayout`: The new layout object that is about to be used by the collection view.

## Discussion

Discussion The default implementation of this method does nothing. Subclasses can override it and use it to prepare for the change in layouts. Special Considerations In OS X 10.11, this method is never called.

## See Also

### Managing Layout Changes

- [preferredLayoutAttributesFitting(_:)](appkit/nscollectionviewelement/preferredlayoutattributesfitting(_:).md)
- [apply(_:)](appkit/nscollectionviewelement/apply(_:).md)
- [didTransition(from:to:)](appkit/nscollectionviewelement/didtransition(from:to:).md)