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Object-Oriented Programming
Example 2–1 Objects-Defined Sample
Dog.h:
class Dog
{ ...
};
main.cpp:
#include "Dog.h"
main()
{
Dog King;
Dog Fifi;
}
Messages
Objects communicate by sending messages. This is done by
calling an object’s methods.
Some principal categories of messages are:
• Constructors: Create objects
• Destructors: Delete objects
• Selectors: Return part or all of an object’s state. For
example, a Get method
• Modifiers: Change part or all of an object’s state. For
example, a Set method
• Iterators: Access multiple element objects within a container
object. For example, an array.
Class
Relationships
Classes can be related in the following ways:
• Simple association: One class is aware of another class. For
example, "Dog object is associated with a Master object." This
is a "Knows a" relationship.
• Composition: One class contains another class as part of its
attributes. For example, "Dog objects contains Leg objects."
This is a "Has a" relationship.
• Inheritance A child class is derived from one or more parent,
or base, classes. For example, "Mutt object derives from
Collie object and Boxer object which both derive from Dog
object." This is an "Is a" relationship. Inheritance enables
the use of polymorphism.
2–8 Architectural Concepts