Decorator design pattern
We'll continue this chapter with the big brother of the Proxy pattern, and maybe, one of the most powerful design patterns of all. The Decorator pattern is pretty simple, but, for instance, it provides a lot of benefits when working with legacy code.
Description
The Decorator design pattern allows you to decorate an already existing type with more functional features without actually touching it. How is it possible? Well, it uses an approach similar to matryoshka dolls, where you have a small doll that you can put inside a doll of the same shape but bigger, and so on and so forth.
The Decorator type implements the same interface of the type it decorates, and stores an instance of that type in its members. This way, you can stack as many decorators (dolls) as you want by simply storing the old decorator in a field of the new one.
Objectives
When you think about extending legacy code without the risk of breaking something, you should think of the Decorator pattern first...
