Dependency Injection with PHP

Dependency Injection with PHP @BastianHofmann

Dependency Injection Dependency Injection Containers Dependency Inversion Dependencies

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http://speakerdeck.com/u/bastianhofmann

Dependency Inversion

http://www.doolwind.com/blog/solid-principles-for-game-developers/

http://qafoo.com/presentations.html

High-level modules should not depend on low level modules but
on abstractions. ”

A B C <<interface>> <<interface>>

A B C <<interface>>

A B Adapter <<interface>> C

Dependency Injection

Constructor

Setter

Method argument

Constructing classes

Beneﬁts

Easier to change

Easier testing

Only test the class, not the dependencies

Mocking

But...

Make it easier with factories

Dependency Injection Container

rg\injektor inspired by google-guice

https://github.com/researchgate/injektor

http://getcomposer.org/ http://packagist.org/

$ cat composer.json

$ wget http://getcomposer.org/composer.phar $ php composer.phar install Installing dependencies -
Installing monolog/monolog (1.1.0) Downloading: 100% ... monolog/monolog suggests installing mlehner/ gelf-php (Allow sending log messages to a GrayLog2 server) Writing lock file Generating autoload files

Creating an instance of a class

PHP 5.5

Automatic creation of dependencies through Typehints

@inject

What classes can be injected?

No constructor

Constructor without arguments

Constructor with arguments that have default values

Injectable constructor

By the way: Property Injection

Singletons with public static getInstance method following the same rules

STOP: Don‘t use Singeltons

Singletons are evil!

Let the DIC take care of instances

@singleton

Passing additional, ﬁxed values to instance

Working with Interfaces

But we can not create an instance of an Interface!

@implementedBy

Named @implementedBy

Providers

@providedBy

Method invocation at DIC

Same rules

And if you don‘t like annotations... ... or want to
integrate 3rd party code

Great! So, how does it work?

Development: Reﬂection

Production: Generated Factory Classes

https://github.com/bashofmann/dic_demo/

https://github.com/symfony/DependencyInjection

https://github.com/zendframework/zf2

Automatic creation of dependencies through Typehints

http://ﬂow3.typo3.org/documentation/guide/partiii/ aspectorientedprogramming.html

class Forum { /** * @FLOW3\Inject
* @var ApplicationLoggerInterface */ protected $applicationLogger; /** * @param Post $post * @return void */ public function deletePost(Post $post) { $this-‐>applicationLogger-‐>log('Removing post'); $this-‐>posts-‐>remove($post); } }

class Forum { /** * Delete a
forum post * * @param Post $post * @return void */ public function deletePost(Post $post) { $this-‐>posts-‐>remove($post); } }

/** * @FLOW3\Aspect */ class LoggingAspect { /**
* @FLOW3\Inject * @var ApplicationLoggerInterface */ protected $applicationLogger; /** * @FLOW3\Before("method(Forum-‐>deletePost())") */ public function logDeletePost(\TYPO3\FLOW3\AOP \JoinPointInterface $joinPoint) { $post = $joinPoint-‐>getMethodArgument('post'); $this-‐>applicationLogger-‐>log('Removing'); } }

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Dependency Injection with PHP

Dependency Injection with PHP

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