Expect everything to change...

Intro

In addition to being responsible for drawing and handling user events, a view instance can act as a container, enclosing other view instances. Those views are linked together creating a view hierarchy. Unlike a class hierarchy, which defines the lineage of a class, the view hierarchy defines the layout of views relative to other views.

The window instance maintains a reference to a single top-level view instance, call the content view. The content view acts as the root of the visible view hierarchy in a window. The view instances enclosed within a view are called subviews. The parent view that encloses a view is referred to as its superview. While a view instance can have multiple subviews, it can have only one superview. In order for a view and its subviews to be visible to the user, the view must be inserted into a window's view hierarchy.

This window's view hierarchy has these parts.

• The window is represented by an NSWindow(aWindow) instance.
• The content view serves as the root of the window's view hierarchy.
• The content View contains a single subview, an instance of a custom class.
• The custom view instance that, in turn has two subviews, an NSButton(viewB) instance, and an NSTextField(viewC) instance.
• The superview for both the button and text field is the NSBox(viewA) object. The custom view container actually encloses the button and text field views.

Relationships among objects in a hierarchy

my thanks to:
http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/CocoaViewsGuide/WorkingWithAViewHierarchy/WorkingWithAViewHierarchy.html