Contents

NSViewController

A controller that manages a view, typically loaded from a nib file.

Declaration

class NSViewController

Overview

View controller management includes:

  • Memory management of top-level objects similar to that performed by the NSWindowController class, taking the same care to prevent reference cycles when controls are bound to the nib file’s owner.

  • Declaring a generic view property, to make it easy to establish bindings in the nib to an object that isn’t yet known at nib-loading time or readily available to the code that’s doing the nib loading.

  • Implementing the key-value binding NSEditor informal protocol, so that apps using a view controller can easily make bound controls in the views commit or discard changes by the user.

In macOS 10.10 and later, a view controller offers a full set of life cycle methods, allowing you to manage the content of a window in a way that is on a par with iOS view controller management. These methods, presented in order here to reflect a typical cycle, are:

View life cycle:

  1. viewDidLoad()

  2. viewWillAppear()

  3. viewDidAppear()

User interaction cycle:

  1. updateViewConstraints()

  2. viewWillLayout()

  3. viewDidLayout()

  4. viewWillDisappear()

  5. viewDidDisappear()

In addition, in macOS 10.10 and later, a view controller participates in the responder chain. You can implement action methods directly in the view controller. Corresponding actions that originate in the view controller’s view proceed up the responder chain and are handled by those methods.

Prior to OS X v10.10, a typical usage pattern for loading a nib file was to subclass NSViewController and override its loadView() method to call [super loadView]. But in macOS 10.10 and later, the loadView() method automatically looks for a nib file with the same name as the view controller. To take advantage of this behavior, name a nib file after its corresponding view controller and pass nil to both parameters of the init(nibName:bundle:) method.

A view controller employs lazy loading of its view: Immediately after a view controller is loaded into memory, the value of its isViewLoaded property is false. The value changes to true after the loadView() method returns and just before the system calls the viewDidLoad() method.

A view controller is meant to be highly reusable, such as for dynamically representing various objects. For example, the addAccessoryController(_:) methods of the NSPageLayout and NSPrintPanel classes take an NSViewController instance as the argument, and set the representedObject property to the NSPrintInfo object that is to be shown to the user. This allows a developer to easily create new printing accessory views using bindings and the NSPrintInfo class’s key-value coding and key-value observing compliance. When the user dismisses a printing dialog, the NSPageLayout and NSPrintPanel classes each send NSEditor messages to each accessory view controller to ensure that the user’s changes have been committed or discarded properly. The titles of the accessories are retrieved from the view controllers and shown to the user in menus that the user can choose from.

Topics

Creating A View Controller

Represented Object

Nib Properties

View Properties

View Property Wrappers

NSEditor Conformance

Using a Storyboard

Responding to View Events

Managing View Layout

Managing Child View Controllers in a Custom Container

Presenting Another View Controller’s Content

Getting Related View Controllers

Configuring an App Extension View Controller

Constants

Initializers

See Also

Content Controllers