mirror of
https://github.com/DesignPatternsPHP/DesignPatternsPHP.git
synced 2025-09-27 14:59:11 +02:00
24 lines
819 B
Markdown
24 lines
819 B
Markdown
# Null Object
|
|
|
|
## Purpose
|
|
|
|
NullOutput is a example of NullObject pattern. It is not formally a Design Pattern by the GoF but it's a schema which appears frequently enough to
|
|
be a pattern. Furthermore it is a really good pattern in my opinion:
|
|
|
|
* the code in the client is simple
|
|
* it reduces the chance of null pointer exception
|
|
* less "if" => less test cases
|
|
|
|
Every time you have a method which returns an object or null, you should return an object or a `NullObject`. With NullObject, you don't need
|
|
a statement like `if (!is_null($obj)) { $obj->callSomething(); }` anymore.
|
|
|
|
## 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
|
|
|
|
 |