---
title: visibleItemsInvalidationHandler
framework: appkit
role: symbol
role_heading: Instance Property
path: appkit/nscollectionlayoutsection/visibleitemsinvalidationhandler
---

# visibleItemsInvalidationHandler

A closure called before each layout cycle to allow modification of the items in the section immediately before they’re displayed.

## Declaration

```swift
var visibleItemsInvalidationHandler: NSCollectionLayoutSectionVisibleItemsInvalidationHandler? { get set }
```