ActionScript 3.0 Cookbook

Chapter 2. Custom Classes

Introduction

Classes are absolutely essential to ActionScript 3.0. This is truer in ActionScript 3.0 than in any earlier release of the language. ActionScript 1.0 was essentially a procedural language with modest object-oriented features. ActionScript 2.0 formalized the object-oriented features and took a big step in the direction of a truly object-oriented language. However, ActionScript 3.0 shifts the core focus of ActionScript so that the basic building block is that of the class. If you are using ActionScript 3.0 with Flex, and the introduction of the minor exception of code being placed within <mx:Script> tags, all ActionScript code must appear within a class. This chapter discusses the fundamentals of writing custom classes in ActionScript 3.0.

Creating a Custom Class

Problem

You want to write a custom class.

Solution

Save a new file with the .as file extension and the filename matching the name of the class. Then add the class definition to the file with the following structure:

package package  {
    public class Class {

    }
}

Discussion

As noted earlier, the class is the basic building block of all ActionScript 3.0-based applications, so it’s essential that you master the basics of writing a class. For starters, all classes must be placed in .as files, which are plain text files saved with an .as file extension. There can be only one public class definition per .as file, and the name of the file must be the same as the name of the class. For example, if you ...