This document discusses Drupal services and provides examples of how to use and customize services. It covers: - Common Drupal services like path, cache, and entity services - Defining services in a module's services.yml file - Overriding existing services by decorating or replacing their class - Creating a custom service for integrating with an external API - Stubbing out an external API service for local testing without hitting the real API

1. Drupal 8 Services
Phil Norton

2. Drupal::service('thing');

3. Wrap objects.
Define a common interface.
Dependency Injection.
Powerful.
Certified awesome.

4. uuid
date
queue
cache
menu
translation
entity
config
cron
renderer
path
route
file_system
plugin

5. $pathManager = Drupal::service('path.alias_manager');
$path = 'somepath';
$normal_path = $pathManager->getPathByAlias($path);

6. $normal_path = Drupal::service('path.alias_manager')
->getPathByAlias('somepath');

7. Services are defined in yml files
<module>.services.yml

8. queue.database:
class: DrupalCoreQueueQueueDatabaseFactory
arguments: ['@database']
path.alias_whitelist:
class: DrupalCorePathAliasWhitelist
tags:
- { name: needs_destruction }
arguments: [path_alias_whitelist, '@cache.bootstrap', '@lock', '@state', '@path.alias_storage']
path.alias_manager:
class: DrupalCorePathAliasManager
arguments: ['@path.alias_storage', '@path.alias_whitelist', '@language_manager', '@cache.data']
path.current:
class: DrupalCorePathCurrentPathStack
arguments: ['@request_stack']

10. Altering Services

11. Problem: Shield module prevents testing of API service on
staging website.
Solution: Poke a hole in the shield!

12. Module shield_override
shield_override.info.yml
src/ShieldOverrideServiceProvider.php
src/ShieldOverride.php

13. <?php
namespace Drupalshield_override;
use DrupalCoreDependencyInjectionContainerBuilder;
use DrupalCoreDependencyInjectionServiceProviderBase;
class ShieldOverrideServiceProvider extends ServiceProviderBase {
public function alter(ContainerBuilder $container) {
// Decorate the shield module to prevent it from triggering on certain
// routes.
$definition = $container->getDefinition('shield.middleware');
$definition->setClass('Drupalshield_overrideShieldOverride');
}
}

14. namespace Drupalshield_override;
use DrupalshieldShieldMiddleware;
use SymfonyComponentHttpFoundationRequest;
class ShieldOverride extends ShieldMiddleware {
public function handle(Request $request, $type = self::MASTER_REQUEST, $catch = TRUE) {
// Get the current request URI.
$currentPath = $request->getRequestUri();
// Get the current method (e.g. GET or POST).
$currentMethod = $request->getMethod();
if (($currentMethod == 'POST' || $currentMethod == 'GET')
&& strstr($currentPath, '/the/soap/service/path) !== FALSE) {
// If we are attempting to access the soap controller via a post HTTP
// method then handle the request without invoking the Shield module.
return $this->httpKernel->handle($request, $type, $catch);
}
// Always handle the request using the default Shield behaviour.
return parent::handle($request, $type, $catch);
}
}

15. Create Your Own

16. <module>.services.yml

17. services:
<service name>:
class: Drupal<full namespace of service class>
arguments: ['@config.factory']

18. PCA Predict Module

19. services:
pcapredict:
class: Drupalpcapredict_integrationPcaPredictPcaPredict
arguments: ['@config.factory']

20. namespace Drupalpcapredict_integrationPcaPredict;
use DrupalCoreConfigConfigFactoryInterface;
use Drupalpcapredict_integrationPcaPredictPcaPredictInterface;
class PcaPredict implements PcaPredictInterface {
protected $pcaPredictKey;
public function __construct(ConfigFactoryInterface $config_factory) {
$this->pcaPredictKey = $config_factory->get('pcapredict_integration.settings')->get('pcapredict_apikey');
}
public function find(array $values, $type = 'json') {
// Load data from the API.
}
public function retrieve(array $values, $type = 'json') {
// Load data from the API.
}
}

21. Problem: Testing PCA Predict needs an API account and
costs money per transaction.
Solution: Create a service override that doesn’t use the API.

22. New module called PCA Predict integration stub
pcapredict_integration_stub.info.yml
src/PcaPredictIntegrationStubServiceProvider.php
src/PcaPredict/PcaPredictStub.php

23. namespace Drupalpcapredict_integration_stub;
use DrupalCoreDependencyInjectionContainerBuilder;
use DrupalCoreDependencyInjectionServiceProviderBase;
class PcaPredictIntegrationStubServiceProvider extends ServiceProviderBase {
public function alter(ContainerBuilder $container) {
// Override the PcaPredict class with a new class.
$definition = $container->getDefinition('pcapredict');
$definition->setClass('Drupalpcapredict_integration_stubPcaPredictPcaPredictStub');
}
}

24. namespace Drupalpcapredict_integration_stubPcaPredict;
use Drupalpcapredict_integrationPcaPredictPcaPredictInterface;
use DrupalCoreConfigConfigFactoryInterface;
class PcaPredictStub implements PcaPredictInterface {
protected $pcaPredictKey;
public function __construct(ConfigFactoryInterface $config_factory) {
$this->pcaPredictKey = $config_factory->get('pcapredict_integration.settings')->get('pcapredict_apikey');
}
public function find(array $values, $type = 'json') {
// Load data from a CSV file.
}
public function retrieve(array $values, $type = 'json') {
// Load data from a CSV file.
}
}

25. find() / retrieve()
API
Address finder

26. find() / retrieve() Address finder

27. Resources
Documentation
https://api.drupal.org/api/drupal/core%21core.api.php/group/container/8.3.x
List of all services
https://api.drupal.org/api/drupal/services