ActionScript: The Definitive Guide

Built-in ActionScript Classes and Objects

We’ve really come a long way since Chapter 1. Our first exposure to the components of ActionScript was a simple perusal of the items under the + button in the Actions panel. Since then, we’ve learned about data and expressions, operators, statements, and functions, and now we’ve explored the concept of classes and objects. It’s time to put the final brush strokes on the picture we’ve been painting of the ActionScript language.

ActionScript comes with a variety of syntactic tools: expressions contain data; operators manipulate data; statements give instructions; and functions group instructions into portable commands. These are tools, but they are just tools. They’re the grammar we use to compose instructions in our scripts. What we’re still missing is subject matter. By now we know perfectly well how to speak ActionScript, but we have nothing to talk about. The built-in classes and objects of ActionScript fill that void.

Built-in Classes

Just as we define our own classes to describe and manipulate objects created according to our specifications, ActionScript defines its own classes of data. A variety of prefabricated classes, including the Object class, are built right into the ActionScript language. The built-in classes can control the physical environment of a Flash movie.

For example, one of the built-in classes, the Color class, defines methods that can detect or set the color of a movie clip. To use these methods, we first create a