ActionScript for Flash MX: The Definitive Guide, Second Edition

This is the Title of the Book, eMatter Edition

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

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Chapter 13: Movie Clips

unloadMovie(x); // If x doesn't exist, x yields undefined, so

// the function operates on the current timeline

unloadMovie(""); // The target is the empty string, so the function operates

// on the current timeline

This can cause some quite unexpected results. Consider what happens if we refer to

a level that doesn’t exist:

unloadMovie(_level1);

If _level1 is empty, the interpreter resolves the reference as though it were an unde-

clared variable. This yields undefined, so the function operates on the current time-

line, not

_level1! So, how do we accommodate this behavior? There are a few

options. We can check for the existence of our target before executing a function on

it:

if (_level1) {

unloadMovie(_level1);

}

Or, we can choose to always use a string to indicate the path to our target. If the path

specified in our string does not resolve to a real clip, the function fails silently:

unloadMovie("_level1");

In some cases, we can use the equivalent numeric function for our operation:

unloadMovieNum(1);

Finally, we can choose to avoid the issue altogether by always using clip methods:

_level1.unloadMovie();

For reference, here are the troublemakers (the ActionScript global functions that take

target parameters):

duplicateMovieClip()

loadMovie()

loadVariables()

print( ...