Описание тега uiviewcontroller

The UIViewController class manages the views in iOS and watch-os apps and mediates the interaction between an app's views, its underlying model objects, and the overall workflow.

View controllers are the foundation of your app’s internal structure. Every app has at least one view controller, and most apps have several. Each view controller manages a portion of your app’s user interface as well as the interactions between that interface and the underlying data. View controllers also facilitate transitions between different parts of your user interface.

To quote from the Overview of the UIViewController Class Reference:

The UIViewController class provides the fundamental view-management model for all iOS apps. You rarely instantiate UIViewController objects directly. Instead, you instantiate subclasses of the UIViewController class based on the specific task each subclass performs. A view controller manages a set of views that make up a portion of your app’s user interface. As part of the controller layer of your app, a view controller coordinates its efforts with model objects and other controller objects—including other view controllers—so your app presents a single coherent user interface.

References:

• View Controller Programming Guide for iOS
• Model-View-Controller introduction in the Cocoa Core Competencies document
• UIViewController Class Reference
• View Controller Catalog for iOS