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# willPopUpNotification

This notification is posted just before a pop-up menu is attached to its window frame.

```
class let willPopUpNotification: NSNotification.Name
```

## Discussion

You can use this notification to lazily construct your part’s menus, thus preventing unnecessary calculations until they are needed. The notification object can be either a pop-up button or its enclosed pop-up button cell. This notification does not contain a `userInfo` dictionary.

To observe this notification using Swift concurrency, use [`NSPopUpButtonCell.WillPopUpMessage`](/documentation/AppKit/NSPopUpButtonCell/WillPopUpMessage).

---

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