FACADE DESIGN PATTERN

Problem

A segment of the client community needs a simplified interface to the overall functionality of a complex subsystem.

Discussion

Facade discusses encapsulating a complex subsystem within a single interface object. This reduces the learning curve necessary to successfully leverage the subsystem. It also promotes decoupling the subsystem from its potentially many clients. On the other hand, if the Facade is the only access point for the subsystem, it will limit the features and flexibility that “power users” may need.

The Facade object should be a fairly simple advocate or facilitator. It should not become an all-knowing oracle or “god” object.

Structure

Facade takes a “riddle wrapped in an enigma shrouded in mystery”, and interjects a wrapper that tames the amorphous and inscrutable mass of software.




Facade:-

The facade class abstracts Packages 1, 2, and 3 from the rest of the application.

Clients:-

The objects using the Facade Pattern to access resources from the Packages.

Example

The Facade defines a unified, higher level interface to a subsystem that makes it easier to use. Consumers encounter a Facade when ordering from a catalog. The consumer calls one number and speaks with a customer service representative. The customer service representative acts as a Facade, providing an interface to the order fulfillment department, the billing department, and the shipping department.