Archive for the 'Decorator' Category

An Enigma Wrapped in a Clear Casing
The Decorator Design Pattern is an enigma wrapped in a perfectly clear casing. I can think of fewer design patterns that are clearer in terms of what they do or seem more practical. By using concrete decorations, you can change an object without touching its structure. You can pick and choose what features you want to add, and your central object (or Concrete Component) is untouched. You want to add another feature? ¡No problema! Just add another decoration. Likewise, if you want to remove an unwanted feature, just remove the decoration you no longer want. All of this changing is accomplished without touching the object all the while the object is effectively changed by the decorations. So updating is simply a matter of changing decorations and/or adding new components to be decorated. (Download all files for program here )

In our book, the most real world practical example was a car dealership where different models of hybrid cars (Components) were set up with different accessories (Decorators) to arrive at a final price. As different models of hybrids became available, they could be added to the components and as different accessories came and went, they could be added to the program without having to disrupt the structure of the program. The pricing of the car was based on both on the base price (Component) and the whistles and bells (Decorators) the buyer selected. Once set up, the site is easy to maintain, update and reuse in a different context.

In this post we want to provide a simple yet usable example that can be modified for your own needs. Many of the simple examples we’ve seen (or created ourselves) have made extensive use of string and numeric variables and/or trace output. Given the fact that practical applications make extensive use of such variables, there’s nothing wrong with that. However, we’ve found that the most difficult part of creating design patterns with ActionScript 3.0 is in making use of graphic materials and movie clips.
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