mirror of
https://github.com/DesignPatternsPHP/DesignPatternsPHP.git
synced 2025-02-24 01:32:22 +01:00
21 lines
760 B
Markdown
21 lines
760 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
|