Setting Up Inheritance for Components
Now that you can sub-class movie clips easily with Components and tie them to user-defined classes, you can create hierarchies of animations that share foundational elements.
The essential idea is that you make your foundational class inherit from MovieClip,
as we have done with triangles, and then sub-classes inherit from the foundational
class (or other sub-classes). Because you must define the foundational class
first, you must use an order number in the foundational class definition:
In your sub-classes, you use order numbers greater than the order number of
parent classes, such as #initclip 1. This ensures
that the foundational element class is defined before the sub-class. To establish
the inheritance, in place of inheriting from MovieClip, you would use a statement
MySubClass.prototype = new FoundationClass();
Now your sub-class (MySubClass) will have all the properties and methods of
the foundation (FoundationClass).
Macromedia's Flash User Interface Components, which include elements such as
a list box, a combo box, a push button, and several more, are great examples
of using component hierarchies. Each element has unique properties and methods
to implement particular behavior, but they all share fundamental style properties
and methods such as enabled/disabled states, sizing, and fonts. Designers can
modify the global style sheet (GlobalStyleFormat) and all the components that
draw from global elements will change. You can create your own composite component
by inheriting from any of these classes, too.
When you create the movie clip for the sub-class, you can either place the parent component within the clip or bring the parent component in programmatically via attachMovie or duplicateMovieClip.
|» Level Intermediate|
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|Jonathan Kaye, PhD, is the President and CTO of Amethyst Research LLC, an award-winning interactive design and engineering firm specializing in the creation of online device simulations. He and David Castillo are the authors of "Flash for Interactive Simulation: How to Construct and Use Device Simulations", to be published by Delmar Thomson Learning in November, 2002 (the accompanying web site will be www.FlashSim.com).|
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