Real World Dependency Injection - phpday

Real World Dependency Injection

Stephan Hochdörfer, bitExpert AG


About me

Stephan Hochdörfer, bitExpert AG

Department Manager Research Labs

enjoying PHP since 1999

[email protected]

@shochdoerfer


What are Dependencies?


Application

Framework add. Libraries



Controller

Service / Model

Datastore(s)

UtilsPHP extensions


Are Dependencies bad?



Dependencies are not bad! They are useful!



Hard-coded dependencies are bad!


Tightly coupled code


No reuse of components


No isolation, not testable!



Development gets overcomplicated!

s


„new“ is evil!

<?phpclass DeletePage extends Mvc_Action_AAction {

private $pageManager;

public function __construct() {$this->pageManager = new PageManager();

}

protected function execute(Mvc_Request $request) {$this->pageManager->delete(

(int) $request->get('pageId'));

}}


„new“ is evil!


„new“ is evil!



public function __construct(PageManager $pm) {$this->pageManager = $pm;

}



}}

"High-level modules should not depend on low-level modules.

Both should depend on abstractions."

Robert C. Martin


Interfaces act as contracts



„new“ is evil!



public function __construct(IPageManager $pm) {$this->pageManager = $pm;

}



}}

How to Manage Dependencies?


Manually resolve dependencies?


Automatic wiring required!

Simple Container vs. Full stacked DI Framework


What is Dependency Injection?



Consumer



Consumer Dependencies



Consumer Dependencies Container



Consumer Dependencies Container


How to inject a Dependency?


Constructor Injection

<?php

class MySampleService implements IMySampleService { /** * @var ISampleDao */ private $sampleDao;

public function __construct(ISampleDao $sampleDao) {$this->sampleDao = $sampleDao;

}}


Setter injection<?php

class MySampleService implements IMySampleService { /** * @var ISampleDao */ private $sampleDao;

public function setSampleDao(ISampleDao $sampleDao){$this->sampleDao = $sampleDao;

}}


Interface injection<?php

interface IApplicationContextAware { public function setCtx(IApplicationContext $ctx);}


Interface injection<?php

class MySampleService implements IMySampleService,IApplicationContextAware { /** * @var IApplicationContext */ private $ctx;

public function setCtx(IApplicationContext $ctx) {$this->ctx = $ctx;

}}



How to wire it all up?


Annotation based wiring<?php

class MySampleService implements IMySampleService { private $sampleDao;

/** * @Inject */ public function __construct(ISampleDao $sampleDao) {

$this->sampleDao = $sampleDao; }}


Annotation based wiring<?php

class MySampleService implements IMySampleService { private $sampleDao;

/** * @Inject * @Named('TheSampleDao') */ public function __construct(ISampleDao $sampleDao) {

$this->sampleDao = $sampleDao; }}

External configuration - XML

<?xml version="1.0" encoding="UTF-8" ?><beans>

<bean id="SampleDao" class="SampleDao"><constructor-arg value="app_sample" /><constructor-arg value="iSampleId" /><constructor-arg value="BoSample" />

</bean>

<bean id="SampleService" class="MySampleService"><constructor-arg ref="SampleDao" />

</bean></beans>


External configuration - YAML

services: SampleDao: class: SampleDao arguments: ['app_sample', 'iSampleId', 'BoSample'] SampleService: class: SampleService arguments: [@SampleDao]


External configuration - PHP<?phpclass BeanCache extends Beanfactory_Container_PHP {

protected function createSampleDao() {$oBean = new SampleDao('app_sample',

'iSampleId', 'BoSample');return $oBean;

}

protected function createMySampleService() {$oBean = new MySampleService(

$this->getBean('SampleDao'));return $oBean;

}}



Ready to unlock the door?

Unittesting made easy


Unittesting made easy<?phprequire_once 'PHPUnit/Framework.php';

class ServiceTest extends PHPUnit_Framework_TestCase { public function testSampleService() {

// set up dependencies $sampleDao = $this->getMock('ISampleDao'); $service = new MySampleService($sampleDao);

// run test case$return = $service->doWork();

// check assertions$this->assertTrue($return);

}}


One class, multiple configurations



Page ExporterPage Exporter

Released / PublishedPages

Released / PublishedPages

WorkingcopyPages

WorkingcopyPages


One class, multiple configurations<?phpabstract class PageExporter { protected function setPageDao(IPageDao $pageDao) { $this->pageDao = $pageDao; }}


One class, multiple configurations<?phpabstract class PageExporter { protected function setPageDao(IPageDao $pageDao) { $this->pageDao = $pageDao; }}

Remember: The contract!



<?phpclass PublishedPageExporter extends PageExporter { public function __construct() { $this->setPageDao(new PublishedPageDao()); }}

class WorkingCopyPageExporter extends PageExporter { public function __construct() { $this->setPageDao(new WorkingCopyPageDao()); }}


"Only deleted code is good code!"Oliver Gierke



One class, multiple configurations<?phpclass PageExporter { public function __construct(IPageDao $pageDao) { $this->pageDao = $pageDao; }}


One class, multiple configurations<?xml version="1.0" encoding="UTF-8" ?><beans>

<bean id="ExportLive" class="PageExporter"><constructor-arg ref="PublishedPageDao" />

</bean>

<bean id="ExportWorking" class="PageExporter"><constructor-arg ref="WorkingCopyPageDao" />

</bean></beans>



<?php

// create ApplicationContext instance$ctx = new ApplicationContext();

// retrieve live exporter$exporter = $ctx->getBean('ExportLive');

// retrieve working copy exporter$exporter = $ctx->getBean('ExportWorking');


One class, multiple configurations II



http://editor.loc/page/[id]/headline/

http://editor.loc/page/[id]/content/

http://editor.loc/page/[id]/teaser/


<?phpclass EditPart extends Mvc_Action_AFormAction {

private $pagePartsManager;private $type;

public function __construct(IPagePartsManager $pm) {$this->pagePartsManager = $pm;

}

public function setType($ptype) {$this->type = (int) $type;

}

protected function process(Bo_ABo $formBackObj) {}

}



One class, multiple configurations II<?xml version="1.0" encoding="UTF-8" ?><beans>

<bean id="EditHeadline" class="EditPart"><constructor-arg ref="PagePartDao" /><property name="Type" const="PType::Headline" />

</bean>

<bean id="EditContent" class="EditPart"><constructor-arg ref="PagePartDao" /><property name="Type" const="PType::Content" />

</bean>

</beans>


Mocking external service access



Booking serviceBooking service WS-Connector

WS-Connector WebserviceWebservice



Booking serviceBooking service WS-Connector

WS-Connector WebserviceWebservice

Remember: The contract!



Booking serviceBooking service FS-Connector

FS-Connector FilesystemFilesystem



Booking serviceBooking service FS-Connector

FS-Connector FilesystemFilesystem

fullfills thecontract!


Clean, readable code


Clean, readable code<?phpclass DeletePage extends Mvc_Action_AAction {


public function __construct(IPageManager $pm) {$this->pageManager = $pm;

}



return new ModelAndView($this->getSuccessView());}

}


No framework dependency


No framework dependency<?phpclass MySampleService implements IMySampleService { private $sampleDao;

public function __construct(ISampleDao $sampleDao) {$this->sampleDao = $sampleDao;

}

public function getSample($sampleId) {try { return $this->sampleDao->readById($sampleId);}catch(DaoException $exception) {}

}}


Benefits

Loose coupling, reuse of components!


Benefits

Can reduce the amount of code!


Benefits

Helps developers to understand the code!


Cons – No JSR330 for PHP

Bucket, Crafty, FLOW3, Imind_Context, PicoContainer, Pimple, Phemto,

Stubbles, Symfony 2.0, Sphicy, Solar, Substrate, XJConf, Yadif, Zend_Di (Proposal), Lion Framework, Spiral Framework, Xyster Framework, …


Cons – Developers need mindshift

Configuration ↔ Runtime


http://joind.in/3002

Image Creditshttp://www.sxc.hu/photo/1028452

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Real World Dependency Injection - phpday