Learning ActionScript 2.0 in Adobe Flash
About ActionScript

About ActionScript

The object-oriented programming (OOP) features in ActionScript 2.0 are based on the ECMAScript 4 Draft Proposal currently in development by ECMA TC39-TG1 (see www.mozilla.org/js/language/es4/index.html). Because the ECMA-4 proposal is not yet a standard, and because it is still changing, ActionScript 2.0 is loosely based on this specification.

ActionScript 2.0 supports all the standard elements of the ActionScript language; it lets you write scripts that more closely adhere to standards used in other object-oriented languages, such as Java. ActionScript 2.0 should be of interest primarily to intermediate or advanced Flash developers who are building applications that require the implementation of classes and subclasses. ActionScript 2.0 also lets you declare the object type of a variable when you create it (see About assigning data types and strict data typing) and provides significantly improved compiler errors (see Error Messages).

Key facts about ActionScript 2.0 include the following points:

• Scripts that use ActionScript 2.0 to define classes or interfaces must be stored as external script files, with a single class defined in each script; that is, classes and interfaces cannot be defined in the Actions panel.
• You can import individual class files implicitly (by storing them in a location specified by global or document-specific search paths and then using them in a script) or explicitly (by using the import command); you can import packages (collections of class files in a directory) by using wildcards.
• Applications developed with ActionScript 2.0 are supported by Flash Player 6 and later.

  CAUTION

  The default publish setting for new files created in Flash CS3 is ActionScript 3.0. If you plan to modify an existing FLA file with ActionScript 1.0 or ActionScript 2.0 to use ActionScript 2.0 syntax, ensure that the FLA file specifies ActionScript 2.0 in its publish settings. If it does not, your file will compile incorrectly, although Flash will not necessarily generate compiler errors.

For more information on using ActionScript 2.0 to write object-oriented programs in Flash, see Classes.

Although Adobe recommends that you use ActionScript 3.0, you can continue to use ActionScript 1.0 and ActionScript 2.0 syntax.

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