NSControl

NSControl is an abstract base class in the AppKit framework of macOS that provides common behavior for interactive controls. It is a subclass of NSView and serves as the parent for widgets such as buttons, text fields, sliders, pop-up menus, and other controls that display a value and support editing or interaction. The primary responsibilities of NSControl are to manage the control's displayed value and to route user input to the application's data model via the target–action mechanism.

A central feature is the target and action pair. Each NSControl can have a target object and an action selector. When the user changes the control’s value, the control sends the action message to its target, typically including the control as the sender. Many controls can be configured to send updates continuously as the user drags or types.

NSControl exposes a range of value-related properties, such as stringValue, intValue, floatValue, doubleValue, and objectValue, as well as generic get/set methods. It also supports Cocoa Bindings, allowing a control’s value and other properties to be bound to model objects or controllers.

In terms of architecture, NSControl historically relies on NSCell for drawing and event handling, though modern, view-based controls in AppKit still inherit the same NSControl interface. Subclasses include NSButton, NSTextField, NSSlider, NSStepper, NSPopUpButton, NSComboBox, NSSegmentedControl, NSColorWell, and NSDatePicker, among others.

NSControl also integrates with macOS accessibility and supports various presentation details such as enabled state, focus ring, and highlighting, depending on the concrete subclass.