Application Sitemap & Directory

Define a family of algorithms, encapsulate each one, and make them interchangeable at runtime.

Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified automatically.

Encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations.

Allow an object to alter its behavior when its internal state changes. The object will appear to change its class.

Pass requests along a chain of handlers. Upon receiving a request, each handler decides either to process the request or to pass it to the next handler in the chain.

Define the skeleton of an algorithm in an operation, deferring some steps to subclasses.

Access the elements of an aggregate object sequentially without exposing its underlying representation.

Reduce chaotic dependencies between objects by restricting direct communications between the objects and forcing them to collaborate only via a mediator object.

Capture and externalize an object’s internal state without violating encapsulation, so that the object can be restored to this state later.

Separate an algorithm from the object structure on which it operates.