User Guide

264 ActionScript: Work with Objects and Classes
Learn about extending existing
classes
The extends keyword in ActionScript 2.0 allows you to use all the
methods and properties of an existing class in a new class. For example, if
you wanted to define a class called Drag that inherited everything from the
MovieClip class, you could use the following:
class Drag extends MovieClip
{}
The Drag class now inherits all properties and methods from the existing
MovieClip class, and you can use MovieClip properties and methods
anywhere within the class definition, as in the following example:
class Drag extends MovieClip
{
// constructor
function Drag ()
{
onPress=doDrag;
onRelease=doDrop;
}
private function doDrag():Void
{
this.startDrag();
}
private function doDrop():Void
{
this.stopDrag();
}
}
NOTE
The following ActionScript is an example only. Do not enter the script in
your lesson FLA file.
NOTE
The Convert to Symbol dialog box now offers a class field in which you
can associate visual objects (such as movie clip) with any class that you
define in ActionScript 2.0.