Chapter 3: Using Symbols, Instances, And Library Assets - MACROMEDIA FLASH MX 2004-USING FLASH Use Manual

CHAPTER 3
Using Symbols, Instances, and Library Assets
A symbol is a graphic, button, or movie clip that you create in Macromedia Flash MX 2004 or
Macromedia Flash MX Professional 2004.
You create the symbol only once; you can then reuse it throughout your document or in other
documents. A symbol can include artwork that you import from another application. Any symbol
that you create automatically becomes part of the library for the current document. For more
information on the library, see "Using the library to manage media assets" on page 17.
This chapter describes how to create symbols and instances in the Flash authoring environment.
You can also create buttons, movie clips, and graphics using the Button Class and MovieClip
Class (use the drawing methods of the MovieClip class to create graphics). See "Button class" and
"MovieClip class"in Flash ActionScript Language Reference.
When you create a symbol in the authoring environment, each symbol has its own Timeline. You
can add frames, keyframes, and layers to a symbol Timeline, just as you can to the main Timeline.
For more information, see "Using the Timeline" in Getting Started with Flash. If the symbol is a
movie clip or a button, you can control the symbol with ActionScript. For more information, see
Chapter 5, "Handling Events" in Using ActionScript in Flash.
An instance is a copy of a symbol located on the Stage or nested inside another symbol.
An instance can be very different from its symbol in color, size, and function. Editing the
symbol updates all of its instances, but applying effects to an instance of a symbol updates only
that instance.
Using symbols in your documents dramatically reduces file size; saving several instances of a
symbol requires less storage space than saving multiple copies of the contents of the symbol. For
example, you can reduce the file size of your documents by converting static graphics, such as
background images, into symbols and then reusing them. Using symbols can also speed SWF file
playback, because a symbol needs to be downloaded to Flash Player only once.
You can share symbols among documents as shared library assets during authoring or at runtime.
For runtime shared assets, you can link assets in a source document to any number of destination
document, without importing the assets into the destination document. For assets shared during
authoring, you can update or replace a symbol with any other symbol available on your local
network. See "Using shared library assets" on page 69.
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