0.6 Xna0110-polymorphism based on overloaded methods

Revised: Thu May 05 15:30:44 CDT 2016

This page is part of a Book titled XNA Game Studio .

Table of Contents

• Table of Contents
• Preface
  • The three main characteristics of an object-oriented program
  • Viewing tip
    • Figures
    • Listings
• General background information
  • What is polymorphism?
  • How does C# implement polymorphism?
  • The class named Object
  • Multiple methods with the same name
  • Compile-time and runtime polymorphism, what's the difference?
  • Every class extends some other class
  • A class hierarchy
  • Methods in the Object class
    • Some methods are overloaded
    • Some methods are meant to be overridden
    • Some methods are meant to be used as is
  • Three distinct forms of polymorphism
  • Method overloading
    • Duplicate method names
    • Compile-time polymorphism
    • Selection based on the argument list
• Preview
  • Keeping it short and simple
  • A sample program
    • Within the class and the hierarchy
    • Class B extends class A, which extends Object
    • Designed to illustrate method overloading
• Discussion and sample code
  • Will discuss in fragments
  • The class named A
    • Redundant code
    • The method named m()
  • The class named B
    • Overloaded methods
  • The driver class
    • Call all three overloaded methods
    • One version is inherited
    • Two versions defined in class B
  • The output
    • Parameters are not displayed
• Run the program
• Run my program
• Summary
• Miscellaneous
• Complete program listing

Preface

This module is one in a collection of modules designed primarily for teaching GAME 1343 Game and Simulation Programming I at Austin Community College in Austin, TX. These modules are intended tosupplement and not to replace the textbook.

An earlier module titled Getting Started provided information on how to get started programming with Microsoft's XNA Game Studio.

The three main characteristics of an object-oriented program

Object-oriented programs exhibit three main characteristics:

• Encapsulation
• Inheritance
• Polymorphism

I have explained encapsulation and inheritance in previous modules. I will begin the explanation of polymorphism in this module. However, polymorphism is acomplex topic and several modules will be required to complete the explanation.

Viewing tip

I recommend that you open another copy of this module in a separate browser window and use the following links to easily find and view the Figuresand Listings while you are reading about them.

Figures

• Figure 1 . Screen output from the project named Polymorph01.

Listings

• Listing 1 . Class A from the project named Polymorph01.
• Listing 2 . Class B from the project named Polymorph01.
• Listing 3 . Class Polymorph01 from the project named Polymorph01.
• Listing 4 . Project Polymorph01.

General background information

What is polymorphism?

The meaning of the word polymorphism is something like one name, many forms .