Design Patterns Explained: A New Perspective on Object-Oriented Design

Summary

The Decorator pattern is a way to add additional function(s) to an existing function dynamically. In practice, it requires building a chain of objects that give the desired behaviors. The first object in this chain is called by a Client that had nothing to do with the building of it. By keeping the creation of the chain independent from its use, the Client object is not affected by new requirements to add functionality.