Decoration with several interface

Question

I am always struggling with decoration + interfaces. Say I have the following \'behavior\' interfaces :

interface IFlyable { void Fly();}
interface ISwimmable {          


        

Answer 1

The Decorator Pattern is not intended for adding new methods to the decorated object. This is what you are trying to do, and it's impossible to do elegantly in a statically-typed language.

What Decorator is useful for is where the interface to the decorators and the decorated component is the same, and the decorator adds a bit of extra functionality to the method either before or after passing the request along the decorator chain.