Minimalist Abstract Decorator | 135Minimalist Abstract Decorator
To get started with the Decorator design pattern, a minimum implementation needs
the following:
- An abstract component
- An abstract decorator
- A concrete component
- Concrete decorators
For the sake of clarity, two decorators will be devised so that you can better see how
the structure works (and it’s closer to the model shown in Figure 4-1.) Of all the
classes devised in this pattern, by far the most important is the initial abstract class
modeling the component. Every other class is subclassed from this initial class.
Abstract Component Class
To begin the process of creating a Decorator design pattern, create a component.
You might think of a component as an undecorated Christmas tree, or even a person
deciding what to wear. It’s simple because all the added features are handled by dec-
orators. Example 4-1 has only a single string variable that will be used to describe the
component. Save the script asComponent.as.
From this point on, all the classes will extend the Component class. Keeping in mind
that the class is an abstract one—or at least is treated as one—its primary function is
to establish a basic structure for the rest of the application. It contains a single vari-
able,information, and a single getter function,getInformation( ). These elements set
up both the concrete components and decorations. Both components and decora-
tions need to display information about their characteristics. A concrete Christmas
tree displays information that lets you know that it’s a Christmas tree instead of
Example 4-1. Component.as
package
{
//Abstract Component in Decorator Design Pattern
//**
//Abstract class
public class Component
{
internal var information:String;
public function getInformation( ):String
{
return information;
}
}
}