<!--
{
  "availability" : [
    "macOS: 10.15.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "AppKit",
  "identifier" : "/documentation/AppKit/NSCollectionLayoutSection/visibleItemsInvalidationHandler",
  "metadataVersion" : "0.1.0",
  "role" : "Instance Property",
  "symbol" : {
    "kind" : "Instance Property",
    "modules" : [
      "AppKit"
    ],
    "preciseIdentifier" : "c:objc(cs)NSCollectionLayoutSection(py)visibleItemsInvalidationHandler"
  },
  "title" : "visibleItemsInvalidationHandler"
}
-->

# visibleItemsInvalidationHandler

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

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

---

Copyright &copy; 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)