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Behavioral/NullObject/index.rst

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+Null Object
+===========
+
+Purpose
+-------
+
+NullObject is not a GoF design pattern but a schema which appears
+frequently enough to be considered a pattern. It has the following
+benefits:
+
+-  Client code is simplified
+-  Reduces the chance of null pointer exceptions
+-  Fewer conditionals require less test cases
+
+Methods that return an object or null should instead return an object or
+``NullObject``. ``NullObject``\ s simplify boilerplate code such as
+``if (!is_null($obj)) { $obj->callSomething(); }`` to just
+``$obj->callSomething();`` by eliminating the conditional check in
+client code.
+
+Examples
+--------
+
+-  Symfony2: null logger of profiler
+-  Symfony2: null output in Symfony/Console
+-  null handler in a Chain of Responsibilities pattern
+-  null command in a Command pattern
+
+UML Diagram
+-----------
+
+.. image:: uml/uml.png
+   :alt: Alt NullObject UML Diagram
+   :align: center
+
+Code
+----
+
+You can also find these code on `GitHub`_
+
+PrintLogger.php
+
+.. literalinclude:: PrintLogger.php
+   :language: php
+   :linenos:
+
+NullLogger.php
+
+.. literalinclude:: NullLogger.php
+   :language: php
+   :linenos:
+
+Service.php
+
+.. literalinclude:: Service.php
+   :language: php
+   :linenos:
+
+LoggerInterface.php
+
+.. literalinclude:: LoggerInterface.php
+   :language: php
+   :linenos:
+
+Test
+----
+
+Tests/LoggerTest.php
+
+.. literalinclude:: Tests/LoggerTest.php
+   :language: php
+   :linenos:
+
+.. _`GitHub`: https://github.com/domnikl/DesignPatternsPHP/tree/master/Behavioral/NullObject