Facade

Facade

Purpose

The primary goal of a Facade Pattern is not to avoid you having to read the manual of a complex API. It's only a side-effect. The first goal is to reduce coupling and follow the Law of Demeter.

A Facade is meant to decouple a client and a sub-system by embedding many (but sometimes just one) interface, and of course to reduce complexity.

• A facade does not forbid you the access to the sub-system
• You can (you should) have multiple facades for one sub-system

That's why a good facade has no new in it. If there are multiple creations for each method, it is not a Facade, it's a Builder or a [Abstract|Static|Simple] Factory [Method].

The best facade has no new and a constructor with interface-type-hinted parameters. If you need creation of new instances, use a Factory as argument.

UML Diagram

Code

You can also find this code on GitHub

Facade.php

.. literalinclude:: Facade.php
   :language: php
   :linenos:

OperatingSystem.php

.. literalinclude:: OperatingSystem.php
   :language: php
   :linenos:

Bios.php

.. literalinclude:: Bios.php
   :language: php
   :linenos:

Test

Tests/FacadeTest.php

.. literalinclude:: Tests/FacadeTest.php
   :language: php
   :linenos: