Object-Oriented Thought Process, The, Second Edition

Polymorphism

Polymorphism literally means many shapes. Although polymorphism is tightly coupled to inheritance, it is often cited separately as one of the most powerful advantages to object-oriented technologies. When a message is sent to an object, the object must have a method defined to respond to that message. In an inheritance hierarchy, all subclasses inherit the interfaces from their superclass. However, because each subclass is a separate entity, each might require a separate response to the same message. For example, consider the Shape class and the behavior called Draw. When you tell somebody to draw a shape, the first question he asks is “What shape?” He cannot draw a shape, as it is an abstract concept (in fact, the Draw() method ...