[Head First Design Patterns] Adapter And Facade Pattern

22 Apr 2022

Adapter Pattern

• class adapter (in language which allow to have multi-inheritance, Adapter inherite both Adaptee and Target)

• object adapter (compose Adaptee object in Adapter to implement Target interface)

Implementation

(github)

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Facade Pattern

• to simplify interface (ie. the bundle of actions in smarthome when somebody back to home)

Design principles

• Principle of least knowledge - talk only to your immediate friends: to prevent the design have a large number of class decouple together (which create a fragtile system) -> we should only invoke methods which belong to:
  • the object itself
  • objects passed in method as parameters
  • any object the method creates or instantiated
  • any component of the object

Implementation

(github)