---
title: "splitViewWillResizeSubviews(_:)"
framework: appkit
role: symbol
role_heading: Instance Method
path: "appkit/nssplitviewdelegate/splitviewwillresizesubviews(_:)"
---

# splitViewWillResizeSubviews(_:)

Notifies the delegate when the split view is about to resize its subviews.

## Declaration

```swift
@MainActor optional func splitViewWillResizeSubviews(_ notification: Notification)
```

## Parameters

- `notification`: A notification named doc://com.apple.appkit/documentation/AppKit/NSSplitView/willResizeSubviewsNotification, which posts before a change to the size of some or all subviews of a split view.

## Discussion

Discussion If the delegate implements this method, the system automatically registers it to receive this notification. The default notification center invokes this method before the split view resizes two of its subviews in response to the repositioning of a divider.

## See Also

### Managing Subviews

- [splitViewDidResizeSubviews(_:)](appkit/nssplitviewdelegate/splitviewdidresizesubviews(_:).md)
- [splitView(_:canCollapseSubview:)](appkit/nssplitviewdelegate/splitview(_:cancollapsesubview:).md)
- [splitView(_:shouldCollapseSubview:forDoubleClickOnDividerAt:)](appkit/nssplitviewdelegate/splitview(_:shouldcollapsesubview:fordoubleclickondividerat:).md)