Facade

Provide a unified interface to a set of interfaces in a subsystem. Facade defines a higher-level interface that makes the subsystem easier to use.

• Facade.
  • knows which subsystem classes are responsible for a request.
  • delegates client requests to appropriate subsystem objects.
• Subsystem classes.
  • implement subsystem functionality.
  • handle work assigned by the Facade object
  • have no knowledge of the facade and keep no reference to it.

• Provides a simple interface to a complex system without reducing the functionality provided by the system.
• Shields clients from complexity of subsystem components.
• Promotes weak coupling between the subsystem and its clients.
• Reduces coupling between subsystems if every subsystem uses its own facade pattern.
• Translates client requests to the subsystems that can fulfill those requests.