NSViewController

NSViewController is a controller class in Apple's AppKit that manages a root NSView and coordinates a portion of a macOS application's user interface. It serves as the macOS counterpart to UIKit's UIViewController, and is used to encapsulate the behavior and data associated with a view hierarchy. An NSViewController owns a view via its view property, which is loaded from a nib/storyboard or created programmatically in loadView. The representedObject property can hold a model object associated with the view.

During its lifecycle, an NSViewController is typically instantiated from a storyboard or programmatically, and its view is loaded when first accessed. Subclasses commonly override loadView to build views programmatically, and override viewDidLoad for setup after loading. The methods viewWillAppear, viewDidAppear, viewWillDisappear, and viewDidDisappear provide hooks for responding to visibility changes.

Containment enables complex interfaces by composing multiple view controllers. An NSViewController can become a child of another controller with containment APIs such as addChildViewController and removeFromParentViewController, and can transition between child controllers with transitionFromViewController:toViewController:duration:options:completion:. Container controllers include NSSplitViewController, NSTabViewController, and NSPageController, as well as container setups in storyboards.

NSViewController interacts with other AppKit components such as NSWindowController and NSStoryboard, and can transfer data via its representedObject property. It plays a central role in modern macOS architecture by enabling modular, reusable UI components and simplifying navigation within window-based apps.