NSMenu

NSMenu is a class in Apple's AppKit framework that represents a menu of actions used by macOS applications. It can function as the app’s main menu in the menu bar, as a contextual or pop-up menu, or as the contents of an NSStatusItem’s menu. A menu is composed of NSMenuItem objects, each of which can have a title, an action to perform, a target object, a keyboard shortcut (keyEquivalent), and a possible submenu (another NSMenu).

Menu items can be enabled or disabled, hidden, or in a checked state. Submenus allow nested structures to organize actions hierarchically. The primary relationship is that an NSMenu contains NSMenuItem instances, and an item’s submenu property may reference another NSMenu, creating a tree-like menu structure.

Creation and use typically involve constructing an NSMenu, adding NSMenuItem objects (with titles and actions), and optionally assigning a target for action messages. Actions are sent when a user selects an item. Validation and dynamic enabling or disabling are commonly handled via NSMenuDelegate methods or by implementing the validateMenuItem(_:) method, often in conjunction with the menu’s autoenablesItems behavior.

Display and placement vary by context. The system menu bar is managed automatically by AppKit, while pop-up or contextual menus can be shown programmatically with methods like popUp(positioning:at:in:) or by associating a menu with an NSStatusItem. NSMenu supports dynamic updates through delegate callbacks such as menuNeedsUpdate:.