Applying Domain Driven Design with Symfony Marek Matulka 16 Apr 2014

Marek Matulka @super_marek Software engineer at SensioLabs UK Photo by @cakper

the easy way

(not applying DDD) the easy way*

Typical Symfony project...

Typical Symfony project... … starts with intention to write: * high quality code * reusable code * portable code * code you’re proud of

No content

Typical Symfony controller... use Symfony\Bundle\FrameworkBundle\Controller\Controller; class RegistrationController extends Controller { public function registerAction($id) { $conference = $this->getDoctrine() ->getRepository(‘AcmeConferenceBundle:Conference’) ->find($id); if ($this->get(‘acme_conference.enrolment.service’) ->enrol($conference, $this->getUser())) { $this->get(‘acme_conference.notification.service’) ->notify($this->getUser(), ‘success’); } } }

Typical Symfony controller... Dependency Injection * used as a service locator Fat controllers * with actions full of business logic

NO TESTS?!

Typical Symfony controller... Over time it gets difficult to change. Then we are afraid to change it.

Typical Project Architecture... Acme\TestBundle\Entity ← Models Acme\TestBundle\Resource\views ← Views Acme\TestBundle\Controller ← Controllers

Typical Project Architecture... Acme\TestBundle\Entity ← Models Acme\TestBundle\Resource\views ← Views Acme\TestBundle\Controller ← Controllers FAT Controllers Thin Models

Typical Symfony project...

Typical Symfony project... ...ends full of: * tightly coupled objects * objects that are difficult to re-use * code you’re afraid to change * code you cannot test

Why it ended like that?

Why it ended like that? * poor understanding of the core domain * bad names * urge to use framework’s goodies * ContainerAware is evil * locked into framework’s structure * Acme\Bundle\TestBundle\Entity

Is there another way?

the right way

(in my humble opinion) the right way*

Forget about the framework

No content

Forget about the framework

namespace Acme\ConferenceBundle\Controller; use Symfony\Bundle\FrameworkBundle\Controller\Controller; class RegistrationController extends Controller { public function registerAction($id) { $conference = $this->getDoctrine() ->getRepository(‘AcmeConferenceBundle:Conference’) ->find($id); if ($this->get(‘acme_conference.enrolment.service’) ->enrol($conference, $this->getUser())) { $this->get(‘acme_conference.notification.service’) ->notify($this->getUser(), ‘success’); $this->redirect(‘registration_successful’) } $this->redirect(‘registration_failed’); } }

Make your dependencies explicit

namespace Acme\ConferenceBundle\Controller; use Symfony\Bundle\FrameworkBundle\Controller\Controller; class RegistrationController extends Controller { public function registerAction($id) { $conference = $this->getDoctrine() ->getRepository(‘AcmeConferenceBundle:Conference’) ->find($id); if ($this->get(‘acme_conference.enrolment.service’) ->enrol($conference, $this->getUser())) { $this->get(‘acme_conference.notification.service’) ->notify($this->getUser(), ‘success’); return $this->redirect(‘registration_successful’); } return $this->redirect(‘registration_failed’); } }

namespace Acme\ConferenceBundle\Controller; use Symfony\Bundle\FrameworkBundle\Controller\Controller; class RegistrationController extends Controller { public function registerAction($id) { $conference = $this->getDoctrine() ->getRepository(‘AcmeConferenceBundle:Conference’) ->find($id); if ($this->get(‘acme_conference.enrolment.service’) ->enrol($conference, $this->getUser())) { $this->get(‘acme_conference.notification.service’) ->notify($this->getUser(), ‘success’); return $this->redirect(‘registration_successful’); } return $this->redirect(‘registration_failed’); } } Repository Response Service Service Value

namespace Acme\ConferenceBundle\Controller; use Symfony\Bundle\FrameworkBundle\Controller\Controller; class RegistrationController extends Controller { public function registerAction($id) { $conference = $this->getDoctrine() ->getRepository(‘AcmeConferenceBundle:Conference’) ->find($id); if ($this->get(‘acme_conference.enrolment.service’) ->enrol($conference, $this->getUser())) { $this->get(‘acme_conference.notification.service’) ->notify($this->getUser(), ‘success’); return $this->redirect(‘registration_successful’); } return $this->redirect(‘registration_failed’); } } ConferenceRepository RedirectResponse ConferenceEnrolment EnrolmentNotification Conference

Use interfaces to describe communication

namespace Acme\ConferenceBundle\Controller; use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route; use Sensio\Bundle\FrameworkExtraBundle\Configuration\ParamConverter; use Acme\Learning\Conference; class RegistrationController { /** * @Route("/conference/{id}/enrol") * @ParamConverter("conference", class="AcmeConferenceBundle:Conference") */ public function registerAction(Conference $conference) { if ($this->get(‘acme_conference.enrolment.service’) ->enrol($conference, $this->getUser())) { $this->get(‘acme_conference.notification.service’) ->notify($this->getUser(), ‘success’); return $this->redirect(‘registration_successful’); } return $this->redirect(‘registration_failed’); } }

namespace Acme\ConferenceBundle\Controller; use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route; use Sensio\Bundle\FrameworkExtraBundle\Configuration\ParamConverter; use Acme\Enrolment\ConferceEnrolment; class RegistrationController { public function __construct(ConferceEnrolment $enrolment) { $this->enrolment = $enrolment; } /** * @Route("/conference/{id}/enrol") * @ParamConverter("conference", class="AcmeConferenceBundle:Conference") */ public function registerAction(Conference $conference) { if ($this->enrolment->enrol($conference, $this->getUser())) { ... } } }

namespace Acme\ConferenceBundle\Controller; use Acme\Enrolment\ConferceEnrolment; class RegistrationController { public function __construct(ConferceEnrolment $enrolment) { $this->enrolment = $enrolment; } public function registerAction(Conference $conference) { $conference = $this->repository->find($id); if ($this->enrolment->enrol($conference, $this->getUser())) { ... } } } $this->container->get(‘security.context’) ->getToken()->getUser();

# src/Acme/ConferenceBundle/Resources/config/services.xml # src/Acme/Learning/Learner.php namespace Acme\Learning; interface Learner { public function isEnrolled(); }

# src/Acme/ConferenceBundle/Entity/User.php namespace Acme\ConferenceBundle\Enity\User; use Acme\Learning\Learner; use Symfony\Component\Security\Core\User\UserInterface; class User implements Learner, UserInterface { ... public function isEnrolled() { ... } ... }

namespace Acme\ConferenceBundle\Controller; use Acme\Learning\Learner; use Acme\Enrolment\ConferceEnrolment; class RegistrationController { public function __construct( Learner $learner, ConferceEnrolment $enrolment ) { $this->learner = $learner; $this->enrolment = $enrolment; } public function registerAction(Conference $conference) { if ($this->enrolment->enrol($conference, $this->learner)) { ... } } }

namespace Acme\ConferenceBundle\Controller; use Acme\Learning\Learner; use Acme\Enrolment\ConferceEnrolment; class RegistrationController { public function __construct( Learner $learner; ConferceEnrolment $enrolment ) { $this->learner = $learner; $this->enrolment = $enrolment; } public function registerAction(Conference $conference) { if ($this->enrolment->enrol($conference, $this->learner)) { ... } } } Interface

namespace Acme\ConferenceBundle\Controller; use Acme\Learning\Learner; use Acme\Enrolment\ConferceEnrolment; use Symfony\Component\HttpFoundation\RedirectResponse; class RegistrationController { ... public function registerAction(Conference $conference) { if ($this->enrolment->enrol($conference, $this->learner)) { return new RedirectResponse(‘success’); } return new RedirectResponse(‘fail’); } }

namespace Acme\ConferenceBundle\Controller; use Acme\Learning\Learner; use Acme\Enrolment\ConferceEnrolment; use Symfony\Component\HttpFoundation\RedirectResponse; use Symfony\Component\Routing\RouterInterface; class RegistrationController { ... public function registerAction(Conference $conference) { if ($this->enrolment->enrol($conference, $this->learner)) { return new RedirectResponse( $this->router->generate(‘enrolment_successful’) ); } return new RedirectResponse( $this->router->generate(‘enrolment_failed’) ); } }

namespace Acme\ConferenceBundle\Controller; ... use Acme\Enrolment\EnrolmentNotifier; class RegistrationController { ... public function registerAction(Conference $conference) { if ($this->enrolment->enrol($conference, $this->learner)) { $this->notifier->notify($this->learner, ‘success’); return new RedirectResponse( $this->router->generate(‘enrolment_successful’)); } return new RedirectResponse( $this->router->generate(‘enrolment_failed’)); } }

am I happy?

namespace Acme\ConferenceBundle\Controller; use Acme\Learning\Learner; use Acme\Enrolment\ConferceEnrolment; use Symfony\Component\HttpFoundation\RedirectResponse; use Symfony\Component\Routing\RouterInterface; use Acme\Enrolment\EnrolmentNotifier; class RegistrationController { public function __construct( Learner $learner, ConferenceEnrolment $enrolment, EnrolmentNotifier $notifier, RouterInterface $router ) { $this->learner = $learner; $this->enrolment = $enrolment; $this->notifier = $notifier; $this->router = $router; } ... Interfaces!

namespace Acme\ConferenceBundle\Controller; use Acme\Learning\Learner; use Acme\Enrolment\ConferceEnrolment; use Symfony\Component\HttpFoundation\RedirectResponse; use Symfony\Component\Routing\RouterInterface; use Acme\Enrolment\EnrolmentNotifier; class RegistrationController { public function __construct( Learner $learner ConferenceEnrolment $enrolment, EnrolmentNotifier $notifier, RouterInterface $router ) { $this->learner = $learner; $this->enrolment = $enrolment; $this->notifier = $notifier; $this->router = $router; } ... Interfaces!

INTERFACES! I SEE INTERFACES EVERYWHERE!

namespace Acme\Enrolment; use Acme\Learning\Learner; use Acme\Learning\Conference; use Acme\Enrolment\ConferceEnrolment; use Acme\Enrolment\EnrolmentNotifier; class ConferenceEnrolmentHandler { public function __construct( ConferceEnrolment $enrolment, EnrolmentNotifier $notifier ) { $this->enrolment = $enrolment; $this->notifier = $notifier; } public function handle(Conference $conference, Learner $learner) { if ($this->enrolment->handle($conference, $learner)) { $this->notifier->notify($learner, ‘success’); return true; } return false; } }

namespace Acme\ConferenceBundle\Controller; use Acme\Learning\Learner; use Symfony\Component\HttpFoundation\RedirectResponse; use Symfony\Component\Routing\RouterInterface; use Acme\Enrolment\ConferenceEnrolmentHandler; class RegistrationController { ... public function registerAction(Conference $conference) { $route = $this->handler->handle($conference, $this->learner) ? ‘enrolment_successful’ : ‘enrolment_failed’; return new RedirectResponse( $this->router->generate($route) ); } }

am I happy?

Project Architecture Acme\Learning Acme\Enrolment Acme\ConferenceBundle Acme\EnrolmentAdapter

Project Architecture Acme\Learning Model Acme\Enrolment Application/Services Acme\DoctrineAdapter Doctrine Acme\EnrolmentBundle Controller/View

(I’ve forgotten about Doctrine!) oops!

# src/Acme/Conference/ConferenceRepository.php namespace Acme\Conference; interface ConferenceRepository { public function find($id); } # src/Acme/DoctrineAdapter/DoctrineConferenceAdapter.php namespace Acme\DoctrineAdapter; use Doctrine\ORM\EntityRepository; use Acme\Conference\ConferenceRepository; class DoctrineConferenceAdapter extends EntityRepository implements ConferenceRepository { // ConferenceRepository::find($id) is already implemented by EntityRepository } # src/Acme/DoctrineAdapter/Resources/mapping/conference.orm.xml

What is Domain Driven Design?

What is Domain Driven Design? Changing folder structure and locations won’t #DDD your project.

What is Domain Driven Design? Fully understanding your domain and describing your business process using the same language as your business.

Layered Architecture Acme\EnrolmentBundle Acme\Enrolment Acme\Learning Acme\DoctrineAdapter User Interface Application Domain Infrastructure

Dependency Inversion “High level modules should not depend on lower level implementation” – Good old Uncle Bob

Controller Services Domain Infrastructure User Interface Dependency Inversion

Controller Services Domain Infrastructure User Interface Dependency Inversion Interfaces!

Controller Services Domain Infrastructure User Interface Dependency Inversion

Controller Services Domain Infrastructure User Interface Dependency Inversion Implementation detail

Don’t mix layers!

Know your domain

Use right tools

@super_marek Questions?

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Thank you! @super_marek