Decorator

• Also known as: Wrapper
• Add responsibilities to objects dynamically
• Attach additional responsibilities to an object dynamically
• Provide a flexible alternative to subclassing for extending functionality

Component

• Defines the interface for objects that can have responsibilities added to them dynamically.

ConcreteComponent

• Defines an object to which additional responsibilities can be attached.

Decorator

• Maintains a reference to a Component object and defines an interface that conforms to Component's interface.

ConcreteDecorator

• Adds responsibilities to the component.