The Decorator Pattern in Action - Implementing the Paper Doll Decorator
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As noted, no interface was created for implementing this application, and so you can see clearly how the concrete component is wrapped by the decorators. Then, on the stage, you can see the effects of the different combinations.
The sequence is:
- Instantiate a concrete component.
Wrap the concrete component in the desired decorator instance using the format:
componentInstance = new DecoratorInstance(componentInstance)
- Apply the getter method (getDressed()) to the concrete component instance initiated to get the fully wrapped values. The values will include those of the concrete component instance and the applied decorations.
Example 4-16 illustrates how to implement the paper doll decorator.
Example 4-16. FashionShow.as
package
{
import flash.display.Loader;
import flash.net.URLRequest;
import flash.display.Sprite;
public class FashionShow extends Sprite
{
var ensemble:Array=new Array();
public function FashionShow()
{
trace("||--Working--||");
var doll:Model = new Sue();
doll=new Hat(doll);
doll=new OrangeDress(doll);
//doll=new BlueDress(doll);
//doll=new Umbrella(doll);
doll=new Bow(doll);
doll=new Muff(doll);
var ready2wear:String=doll.getDressed();
sewingMachine(ready2wear);
for (x=0; x < ensemble.length; x++)
{
clothesOn(ensemble[x]);
}
}
private function sewingMachine(wardrobe:String):Array
{
ensemble=wardrobe.split("~");
ensemble.shift();
return ensemble;
}
private function clothesOn(outfit:String)
{
var clothier:Loader=new Loader();
var item:String="clothes/" + outfit + ".gif";
var getItem:URLRequest=new URLRequest(item);
clothier.load(getItem);
this.addChild(clothier);
}
}
}
Once you’ve got everything ready to go, you’ll need some GIF files. The model (concrete component) should be an image of a doll that you will clothe with the Decorator pattern. Each filename needs to be the name of the value assigned to thewhatToWearvariable in the concrete component or decorator listing, minus the tilde (~) character. For example, the concrete component,Sue,whatToWearvariable is assigned the string value “~sue” and so the GIF filename for that component would besue.gif. The decoratorBlueDresshas awhatToWearvalue of “~bluedress,” and so the image with the blue dress would be namedbluedress.gif. Place all the GIF files, including the file representing the doll model, in a folder namedclothes.
Finally, open up a new Flash document and set the stage dimensions to 300 × 650. In the Properties panel’s Document class window, type in FashionShow. The size and shape of your stage will depend on the size of the paper dolls you use.
Figure 4-6 shows two different combinations of decorations on the paper doll. The image on the left decorates with the hat, bow, orange dress, and muff, while the second is the blue dress, the bow and an umbrella. Each appears very different just by changing the combination of decorations.
Figure 4-6. Paper doll with two different decoration sets
Instead of paper dolls, any component could be decorated with any characteristics. Also, you can include more than a single property or method in a decoration. In the next section, we’ll take a look at adding additional properties with the Decorator design pattern.
Please check back next week for the continuation of this article.
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 This article is excerpted from chapter four of ActionScript 3.0 Design Patterns Object Oriented Programming Techniques, written by William B. Sanders and Chandima Cumaranatunge (O'Reilly, 2007 ISBN: 0596528469). Check it out today at your favorite bookstore. Buy this book now.
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