0.5 Xna0108-inheritance in c#  (Page 11/7)

Revised: Thu May 05 14:27:52 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
  • A new class can extend an existing class
    • What is inherited?
    • The superclass remains viable
    • A hierarchy of classes
  • Members of the System.Object class
    • The Button class
    • The Object class is the default superclass
    • An orderly hierarchy
  • The airship hierarchy
    • The Balloon class
    • The Airplane class
    • Three types of objects
    • From the general to the specialized
  • Single and multiple inheritance
  • The ISA relationship
  • The HASA relationship
• Preview
  • The airship hierarchy
• Discussion and sample code
  • Will explain in fragments
  • Four class definitions
    • The Airship class
    • The Balloon class
      • The new material
      • The effect of extending a class
    • Airship extends Object
    • The beginning of the Driver class
      • Code common to all four classes
      • Instantiate a new Balloon object
      • Set properties in the Balloon object
      • Get and display property values
      • The program output
    • The remaining code
    • No sharing of properties
• 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 will explain and illustrate inheritance along with some related topics in this module.

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 . Output from the program named Airship01.

Listings

• Listing 1 . The Airship class.
• Listing 2 . The Balloon class.
• Listing 3 . The beginning of the Driver class.
• Listing 4 . The program named Airship01.

General background information

The first of the three major characteristics of an object-oriented program is encapsulation . I explained encapsulation in an earlier module. The second of the three is inheritance , followed by polymorphism . I will explain inheritance in this module and will explain polymorphism in a future module.

A new class can extend an existing class

A class can be defined to inherit the properties, events, and methods of another class. From a syntax viewpoint, this is accomplished using the : (colon) operator (see Listing 2 ).