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 1: A Gentle Introduction for Nonprogrammers

In natural language, this tells the interpreter, “When the mouse button is released

over the

rotateButton object, execute the rotate function.” The rotate function might

look like this:

function rotate ( ) {

this._parent._rotation = 45;

}

A function that is executed when an event occurs is known as a callback function.As

we’ll learn in Chapter 10, within a callback function, the keyword

this refers to the

object that defined the event handler (in our case, rotateButton). In the case of a but-

ton reacting to a mouseclick,

this refers to the button that was clicked. Using object-

oriented syntax, the movie clip in which the button resides is referred to as

this.

_parent

(the movie clip is the button’s _parent because it contains the button).

Finally, we set the rotation of the parent movie clip to 45 degrees by assigning 45 to

this._parent._rotation:

this._parent._rotation = 45;

This literally translates to, “Set the rotation of this button’s parent movie clip to 45

degrees.”

Our sample button event handler is commonly written more succinctly as:

rotateButton.onRelease = function ( ) {

this._parent._rotation = 45;

};

Event-based programs are always running an event loop, ready to react to the next

event. Events are crucial to interactivity. ...