Facade

Intent

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

Class diagram of the original GoF pattern

Improvement in MixJuice

Solved Problem(s)

Information hiding problem

Hiding of subsystem classes from clients is not supported by OLD object-oriented languages. (This problem is mentioned at p.188,line.33-37 in the GoF book.)

Used programming technique(s)

Namespace separation.

Consequences

• (+) Subsystem classes are hidden from clients.

Structure and pseudo code

module subsystem {
  define class C1 { ...  }
  define class C2 { ...  }
  ...
}

module facade {
  define class Facade {
    define abstract void easy_operation();
  }
}

module facade.implementation extends facade, subsystem {
  class Facade {
    void easy_operation() { ... }
  }
}

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