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89 lines
2.1 KiB
ReStructuredText
89 lines
2.1 KiB
ReStructuredText
`Dependency Injection`__
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========================
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Purpose
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-------
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To implement a loosely coupled architecture in order to get better
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testable, maintainable and extendable code.
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Usage
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-----
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Configuration gets injected and ``Connection`` will get all that it
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needs from ``$config``. Without DI, the configuration would be created
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directly in ``Connection``, which is not very good for testing and
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extending ``Connection``.
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Notice we are following Inversion of control principle in ``Connection``
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by asking ``$config`` to implement ``Parameters`` interface. This
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decouples our components. We don't care where the source of information
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comes from, we only care that ``$config`` has certain methods to
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retrieve that information. Read more about Inversion of control
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`here <http://en.wikipedia.org/wiki/Inversion_of_control>`__.
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Examples
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--------
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- The Doctrine2 ORM uses dependency injection e.g. for configuration
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that is injected into a ``Connection`` object. For testing purposes,
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one can easily create a mock object of the configuration and inject
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that into the ``Connection`` object
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- Symfony and Zend Framework 2 already have containers for DI that
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create objects via a configuration array and inject them where needed
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(i.e. in Controllers)
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UML Diagram
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-----------
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.. image:: uml/uml.png
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:alt: Alt DependencyInjection UML Diagram
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:align: center
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Code
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----
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You can also find these code on `GitHub`_
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AbstractConfig.php
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.. literalinclude:: AbstractConfig.php
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:language: php
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:linenos:
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Parameters.php
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.. literalinclude:: Parameters.php
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:language: php
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:linenos:
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ArrayConfig.php
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.. literalinclude:: ArrayConfig.php
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:language: php
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:linenos:
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Connection.php
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.. literalinclude:: Connection.php
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:language: php
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:linenos:
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Test
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----
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Tests/DependencyInjectionTest.php
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.. literalinclude:: Tests/DependencyInjectionTest.php
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:language: php
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:linenos:
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Tests/config.php
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.. literalinclude:: Tests/config.php
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:language: php
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:linenos:
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.. _`GitHub`: https://github.com/domnikl/DesignPatternsPHP/tree/master/Structural/DependencyInjection
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.. __: http://en.wikipedia.org/wiki/Dependency_injection
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