Graphics Programs Reference
In-Depth Information
A subclass adds methods and instance variables to extend the behavior of its superclass.
For example,
NSMutableArray
extends
NSArray
's ability to hold pointers to objects
by adding the ability to dynamically add and remove objects.
A subclass can also override methods of its superclass. For example, sending the
de-
scription
message to an
NSObject
returns the object's class and its address in
memory, like this:
<QuizViewController: 0x4b222a0>
.
