ActionScript for Flash MX: The Definitive Guide, Second Edition

This is the Title of the Book, eMatter Edition

Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.

OOP Quick Reference

|

315

The following code adds a scrollToBottom( ) method to the TextField class:

TextField.prototype.scrollToBottom = function ( ) {

this.scroll = this.maxscroll;

};

The following code creates a subclass of the XML class:

function CustomXML (src) {

super(src);

}

CustomXML.prototype = new XML( );

Some built-in classes actually require the execution of their constructor function as

part of the setup for new objects. When in doubt, always invoke the superclass con-

structor as shown in our previous examples. Note that not all built-in classes can be

subclassed, because some built-in classes (e.g., TextField, Button) are tied to physical

objects on screen. See each class entry in the Language Reference for details.

Many, many more examples of extending the built-in classes and objects can be

found on the developer community site [PROTO]type:

http://www.layer51.com/proto/

OOP Quick Reference

We’ve covered a lot of material in this chapter. For review and reference, here’s a

quick-and-dirty overview of OOP techniques in ActionScript. At the end, you’ll find

a template for creating a new OOP application.

To create a class:

function ClassName (param1, param2) {

// ...constructor code goes here...

}

To create instance properties for a class:

function ClassName (param1, param2) {

// ...