ActionScript 3.0 Design Patterns.pdf - VideoTutorials-bg.com

Applying a Simple Decorator Pattern in Flash:
Paper Doll
You can move from a conceptual example to a concrete one with a computerized
paper doll game. The paper doll component is the doll being dressed, and the decorations
are clothing items selected for the doll. Using ActionScript’s new Loader class,
different GIF files are used to decorate a base GIF image of a Victorian paper doll. As
in the previous abstract example, this example uses a single concrete component and
several decorations.
This concrete example does not have an interface—keeping the focus on the application’s
use of a Decorator pattern. However, it does have a graphic output so you can
see the pattern’s ultimate output. (Later in this chapter, there’s an example with a
full interface.)
Setting Up the Component Class
The first class is the component class, Model. From this, all other classes are subclasses.
It’s very simple but key to the success of the application. As you can see, it’s
very close to the previous abstract Decorator. It consists of a method, getDressed( ),
and a string variable, whatToWear, as shown in Example 4-7. Save the file as Model.as.
Example 4-7. Model.as
package
{
//Abstract class
public class Model
{
protected var whatToWear:String;
public function getDressed( ):String
{
return whatToWear;
}
}
}
Keep in mind that Example 4-7 should be treated as an abstract class. So the method
getDressed( ) needs to be created as an override public function for it to work the
way we want. However, the property whatToWear doesn’t need to be changed from its
inherited characteristics.
Decorator Class: Dressing the Dolls
Example 4-8 is the abstract Decorator class, Dresser, which extends the component
class, Model. The major contribution here is simply re-implementing the getDressed( )
method with a reference to the inherited whatToWear property.
Applying a Simple Decorator Pattern in Flash: Paper Doll | 141