252 Classes
For more information on class members (also called static properties), see “Static methods and
properties” on page 249.
A sample file on your hard disk demonstrates how to create a dynamic menu with XML data
and a custom class file. The sample calls the ActionScript
XmlMenu() constructor and passes it
two parameters: the path to the XML menu file and a reference to the current timeline. The
rest of the functionality resides in a custom class file, XmlMenu.as.
You can find the sample source file, xmlmenu.fla, in the Samples folder on your hard disk.
■ On Windows, browse to boot drive\Program Files\Macromedia\Flash 8\Samples and
Tutorials\Samples\ActionScript\XML_Menu.
■ On the Macintosh, browse to Macintosh HD/Applications/Macromedia Flash 8/Samples
and Tutorials/Samples/ActionScript/XML_Menu.
Using the Singleton design pattern
A common way to use class members is with the Singleton design pattern. A design pattern
defines a formal approach for structuring your code. Typically, you might structure a design
pattern as a solution for a common programming problem. There are many established design
patterns, such as Singleton. The Singleton design pattern makes sure that a class has only one
instance and provides a way of globally accessing the instance. For detailed information on the
Singleton design pattern, see www.macromedia.com/devnet/mx/coldfusion/articles/
design_patterns.html.
Often you encounter situations when you need exactly one object of a particular type in a
system. For example, in a chess game, there is only one chessboard, and in a country, there is
only one capital city. Even though there is only one object, you should encapsulate the
functionality of this object in a class. However, you might need to manage and access the one
instance of that object. Using a global variable is one way to do this, but global variables are
not desirable for most projects. A better approach is to make the class manage the single
instance of the object itself using class members. The following example shows a typical
Singleton design pattern usage, where the Singleton instance is created only once.
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