Decorator

The decorator pattern is a structural pattern Adapter, Bridge, Composite, Decorator, Facade, Flyweight, Proxy that allows behavior to be added to an individual object, dynamically, without affecting the behavior of other objects from the same class. The decorator pattern is often useful for adhering to the Single Responsibility Principle, as it allows functionality to be divided between classes with unique areas of concern. Decorator use can be more efficient than subclassing, because an object's behaviour can be augmented without defining an entirely new object.

Overview

What problems can it solve?
• Responsibilities should be added to (and removed from) an object dynamically at run-time.
• A flexible alternative to subclassing for extending functionality should be provided.

Define Decorator objects that
1. implement the interface of the extended (decorated) object (Component) transparently by forwarding all requests to it
2. perform additional functionality before/after forwarding a request.

This allows working with different Decorator objects to extend the functionality of an object dynamically at run-time.