---
title: willResizeSubviewsNotification
framework: appkit
role: symbol
role_heading: Type Property
path: appkit/nssplitview/willresizesubviewsnotification
---

# willResizeSubviewsNotification

A notification that posts before a change to the size of some or all subviews of a split view.

## Declaration

```swift
class let willResizeSubviewsNotification: NSNotification.Name
```

## Discussion

Discussion The notification object consists of the NSSplitView object about to resize its subviews. The userInfo dictionary includes the NSSplitViewDividerIndex key that contains the index of the divider that the split view or the user moves. If the system sends the notification because the user drags a divider, the dictionary also includes the NSSplitViewUserResizeKey key with a value of 1. To observe this notification using Swift concurrency, use NSSplitView.WillResizeSubviewsMessage.

## See Also

### Managing Notifications

- [didResizeSubviewsNotification](appkit/nssplitview/didresizesubviewsnotification.md)