Applying Domain Driven Design when building Drupal modules with Symfony components

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Applying DDD when building Drupal modules using Symfony components Marek Matulka

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Who am I?

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Marek Matulka @super_marek mareg

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Software Engineer at

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Background

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Requirement CMS - manage corporate website

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Requirement CMS - manage corporate website - manage other brands’ websites

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Requirement CMS - manage corporate website - manage other brands’ websites - build seasonal microsites

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Requirement CMS - manage corporate website - manage other brands’ websites - build seasonal microsites - integrate with Magento store

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Why Drupal? - open source CMS

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Why Drupal? - open source CMS - easy to install and manage

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Why Drupal? - open source CMS - easy to install and manage - most required functionality available out of the box

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Why Drupal? - open source CMS - easy to install and manage - most required functionality available out of the box - easy to extend

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Why Drupal 7?

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What is Symfony?

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is a powerful framework

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Doctrine ORM Twig

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set of decoupled components

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Domain Driven Design

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In order to create a good software, you have to know what the software is all about. – Eric Evans

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How do we learn?

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Stakeholders

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Ask for examples... ...write stories!

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Vocabulary

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Ubiquitous Language Ubiquitous Language

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Ubiquitous Language Ubiquitous Language Domain Expert Analyst Tester Developer Developer

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Ubiquitous Language Ubiquitous Language Domain Expert Analyst Tester Developer Developer Application Code Acceptance Criteria Specs and documentation

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Example?

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Example Feature: In order to see correct prices As a visitor I need to be able to locate the nearest depot Scenario: Given I am visiting a product page for the first time And I got prompted to locate my nearest depot When I enter my post code Then I should see my local depot information

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Domain namespace Acme\Depot; interface DepotLocator { /** * @param string $postcode * * @return Depot */ public function locateDepot($postcode); }

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Implementation namespace Acme\MagentoAdapter; use Acme\Depot\DepotLocator; class MagentoDepotLocator implements DepotLocator { public function locateDepot($postcode) { return $this->entityMapper->mapDepot( $this->clientAdapter->findDepotByPostcode($postcode) );

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why interface?

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Layered Architecture “High level modules should not depend on lower level implementation” – Robert C. Martin User Interface Application Domain Infrastructure

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Dependency Inversion Policy Layer Policy Service Mechanism Layer Mechanism Service Utility Layer

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Layered Architecture User Interface Application Domain Infrastructure

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Layered Architecture User Interface Application Domain Infrastructure

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Clean Architecture Entities Use Cases Controllers Web

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Clean Architecture Entities Use Cases Controllers Web Framework Drivers Interface Adapters Application Business Rules Enterprise Business Rules

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Hexagonal Architecture UI Adapter Log Adapter Data Storage Adapter External Data Adapter Application Domain

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Hexagonal Architecture Acme\Depot\DepotLocator Acme\MagentoAdapter\MagentoDepotLocator

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Hexagonal Architecture Acme\Depot\DepotLocator Acme\MagentoAdapter\MagentoDepotLocator port adapter

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Why clean architecture?

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Why clean architecture? - your code is clean(er)

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Why clean architecture? - your code is clean - decoupled from framework

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Why clean architecture? - your code is clean - decoupled from framework - reusable

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Why clean architecture? - your code is clean - decoupled from framework - reusable - easy to test

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Why clean architecture? - your code is clean - decoupled from framework - reusable - easy to test - easier to maintain

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Why clean architecture? - your code is clean - decoupled from framework - re-usable - easy to test - easier to maintain - easier to change

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When to use DDD?

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When to use DDD? - complex domain

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When to use DDD? - complex domain - access to domain experts

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When to use DDD? - complex domain - access to domain experts - iterative, long term process

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When to use DDD? - complex domain - access to domain experts - iterative, long term process - OO design

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When not to use DDD?

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When not to use DDD? - simple domain

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When not to use DDD? - simple domain - data centric domains

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When not to use DDD? - simple domain - data centric domains - prototyping

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Symfony with Drupal 7

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composer.json "require": { "php": ">=5.4.0", "symfony/console": "~2.5", "drush/drush": "7.*@dev", "symfony/finder": "~2.5", "symfony/dependency-injection": "~2.5", "symfony/config": "~2.5", "symfony/filesystem": "~2.6", "doctrine/dbal": "~2.5", "rhumsaa/uuid": "~2.8" },

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AppKernel.php public function boot() { $this->container = new ContainerBuilder(); $this->container->registerExtension(new ApplicationExtension()); $loader = new YamlFileLoader($this->container, new FileLocator('app/config')); $loader->load('parameters.yml'); $loader = new XmlFileLoader($this->container, new FileLocator('/Resources/config')); $loader->load('services.xml'); $this->container->compile(); } public function getContainer() { return $this->container; }

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settings.php require_once DRUPAL_ROOT . '/../vendor/autoload. php'; $kernel = new \Acme\Application\Kernel(); $kernel->boot(); $conf['di_container'] = $kernel->getContainer();

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database.php $databases = [ 'default' => [ 'default' => [ 'database' => $conf['di_container']->getParameter('database.name'), 'username' => $conf['di_container']->getParameter('database.username'), 'password' => $conf['di_container']->getParameter('database.password'), 'host' => $conf['di_container']->getParameter('database.host'), 'port' => $conf['di_container']->getParameter('database.port'), 'driver' => 'mysql', 'prefix' => '', ], ], ];

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depot_locator.module function get_depot_json($postcode) { global $conf; $depotEntity = $conf['di_container']->get('acme.depot_locator') ->locateDepot($postcode); $depot = [ 'code' => $depotEntity->getCode(), 'name' => $depotEntity->getName(), 'postcode' => $depotEntity->getPostcode(), ]; return ['depot' => $depot]; }