title: Why do we need the decorator in the decorator design pattern?
body: <p>Presuming I have a class named <code>A</code>, and I want to use the decorator design pattern. Correct me if I'm wrong, but for that to work , we'll need to create a decorator class, say <code>ADecorator</code>, which will hold a reference to an <code>A</code> instance, and all the other decorators will extend this to add functionality.</p>
  
  <p>I don't understand why do we have to create a decorator class, instead of using an <code>A</code> instance?</p>