ActionScript for Flash MX: The Definitive Guide, Second Edition

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

Variable Scope

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and then we check the value of day inside circle:

trace(day);

the Output window displays “Friday” (the timeline variable’s value), not “Monday”

(the global variable’s value). For more information on global variables, see

_global in

the Language Reference.

Though true global variables were not supported in Flash 5, it was possible to simu-

late them using the Object class or MovieClip class. To create a variable that is avail-

able on all timelines in Flash 5, use the following statement:

MovieClip.prototype.myGlobalVariable = myValue;

For example:

MovieClip.prototype.msg = "Hello world";

Alternatively, assign the variable as a property of Object, as follows:

Object.msg = "Hello world";

Then, from any other timeline, access msg like this:

trace(Object.msg);

We discuss this technique (and the reason it works) in “The end of the inheritance

chain,” in Chapter 12. In Flash MX, the

_global object is the preferred way to store

global variables.

Accessing Variables on Different Timelines

Even though variables on one timeline are not accessible directly to the scripts on

other timelines, they are accessible indirectly. To create, retrieve, or assign a variable

on a separate timeline, we use dot syntax, a standard notation common to object-ori-

ented programming languages such as Java, ...