menuNeedsUpdate

menuNeedsUpdate is a delegate method of the NSMenuDelegate protocol in macOS AppKit. It is invoked just before a menu is shown, giving the delegate an opportunity to refresh or rebuild the menu’s items. This is especially useful for dynamic or context-sensitive menus whose contents depend on the current state of the application, such as a Recent Files submenu, a list of open documents, or actions that vary with context.

Implementation typically involves the menu’s delegate clearing existing items and repopulating the menu with up-to-date choices. In Objective-C, the method signature is - (void)menuNeedsUpdate:(NSMenu *)menu;. In Swift, it is implemented as func menuNeedsUpdate(_ menu: NSMenu). The provided menu parameter is the menu that will be displayed, so updates should modify its items directly, often by removing all items and then adding new NSMenuItem instances reflecting current data.

Because this callback is part of the UI update cycle, these updates should be performed on the main thread and be kept efficient to avoid visible lag when the menu opens. The method is optional; if the delegate does not implement it, AppKit will not perform dynamic updates for that menu.

Relation to other mechanisms: menuNeedsUpdate is a delegate callback rather than a notification. It is specifically intended for refreshing content, whereas menuWillOpen is a separate notification that is posted when a menu is about to be shown. Understanding the distinction helps in choosing the appropriate hook for dynamic menu content.

See also: NSMenu, NSMenuDelegate, menuWillOpen.