Observer__

Purpose

To implement a publish/subscribe behaviour to an object, whenever a "Subject" object changes its state, the attached "Observers" will be notified. It is used to shorten the amount of coupled objects and uses loose coupling instead.

Examples

• a message queue system is observed to show the progress of a job in a GUI

Note

PHP already defines two interfaces that can help to implement this pattern: SplObserver and SplSubject.

UML Diagram

.. image:: uml/uml.png :alt: Alt Observer UML Diagram :align: center

Code

You can also find this code on GitHub_

User.php

.. literalinclude:: User.php :language: php :linenos:

UserObserver.php

.. literalinclude:: UserObserver.php :language: php :linenos:

Test

Tests/ObserverTest.php

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

.. _GitHub: https://github.com/DesignPatternsPHP/DesignPatternsPHP/tree/main/Behavioral/Observer .. __: http://en.wikipedia.org/wiki/Observer_pattern