How to Manage Common Dependencies with Parent Services
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How to Manage Common Dependencies with Parent Services
As you add more functionality to your application, you may well start to
have related classes that share some of the same dependencies. For example,
you may have multiple repository classes which need the
doctrine.orm.entity_manager
service and an optional logger
service:
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// src/AppBundle/Repository/BaseDoctrineRepository.php
namespace AppBundle\Repository;
// ...
abstract class BaseDoctrineRepository
{
protected $entityManager;
protected $logger;
public function __construct(EntityManagerInterface $manager)
{
$this->entityManager = $manager;
}
public function setLogger(LoggerInterface $logger)
{
$this->logger = $logger;
}
// ...
}
Your child service classes may look like this:
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// src/AppBundle/Repository/DoctrineUserRepository.php
namespace AppBundle\Repository;
use AppBundle\Repository\BaseDoctrineRepository
// ...
class DoctrineUserRepository extends BaseDoctrineRepository
{
// ...
}
// src/AppBundle/Repository/DoctrinePostRepository.php
namespace AppBundle\Repository;
use AppBundle\Repository\BaseDoctrineRepository
// ...
class DoctrinePostRepository extends BaseDoctrineRepository
{
// ...
}
Just as you use PHP inheritance to avoid duplication in your PHP code, the service container allows you to extend parent services in order to avoid duplicated service definitions:
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services:
AppBundle\Repository\BaseDoctrineRepository:
abstract: true
arguments: ['@doctrine.orm.entity_manager']
calls:
- [setLogger, ['@logger']]
AppBundle\Repository\DoctrineUserRepository:
# extend the AppBundle\Repository\BaseDoctrineRepository service
parent: AppBundle\Repository\BaseDoctrineRepository
AppBundle\Repository\DoctrinePostRepository:
parent: AppBundle\Repository\BaseDoctrineRepository
# ...
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<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://symfony.com/schema/dic/services
http://symfony.com/schema/dic/services/services-1.0.xsd">
<services>
<service id="AppBundle\Repository\BaseDoctrineRepository" abstract="true">
<argument type="service" id="doctrine.orm.entity_manager" />
<call method="setLogger">
<argument type="service" id="logger" />
</call>
</service>
<!-- extends the AppBundle\Repository\BaseDoctrineRepository service -->
<service id="AppBundle\Repository\DoctrineUserRepository"
parent="AppBundle\Repository\BaseDoctrineRepository"
/>
<service id="AppBundle\Repository\DoctrinePostRepository"
parent="AppBundle\Repository\BaseDoctrineRepository"
/>
<!-- ... -->
</services>
</container>
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use AppBundle\Repository\DoctrineUserRepository;
use AppBundle\Repository\DoctrinePostRepository;
use AppBundle\Repository\BaseDoctrineRepository;
use Symfony\Component\DependencyInjection\ChildDefinition;
use Symfony\Component\DependencyInjection\Reference;
$container->register(BaseDoctrineRepository::class)
->setAbstract(true)
->addArgument(new Reference('doctrine.orm.entity_manager'))
->addMethodCall('setLogger', array(new Reference('logger')))
;
// extend the AppBundle\Repository\BaseDoctrineRepository service
$definition = new ChildDefinition(BaseDoctrineRepository::class);
$definition->setClass(DoctrineUserRepository::class);
$container->setDefinition(DoctrineUserRepository::class, $definition);
$definition = new ChildDefinition(BaseDoctrineRepository::class);
$definition->setClass(DoctrinePostRepository::class);
$container->setDefinition(DoctrinePostRepository::class, $definition);
// ...
In this context, having a parent
service implies that the arguments
and method calls of the parent service should be used for the child services.
Specifically, the EntityManager
will be injected and setLogger()
will
be called when AppBundle\Repository\DoctrineUserRepository
is instantiated.
All attributes on the parent service are shared with the child except for
shared
, abstract
and tags
. These are not inherited from the parent.
Note
If you have a _defaults
section in your file, all child services are required
to explicitly override those values to avoid ambiguity. You will see a clear
error message about this.
Tip
In the examples shown, the classes sharing the same configuration also extend from the same parent class in PHP. This isn't necessary at all. You can just extract common parts of similar service definitions into a parent service without also extending a parent class in PHP.
Overriding Parent Dependencies
There may be times where you want to override what service is injected for one child service only. You can override most settings by simply specifying it in the child class:
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services:
# ...
AppBundle\Repository\DoctrineUserRepository:
parent: AppBundle\Repository\BaseDoctrineRepository
# overrides the public setting of the parent service
public: false
# appends the '@app.username_checker' argument to the parent
# argument list
arguments: ['@app.username_checker']
AppBundle\Repository\DoctrinePostRepository:
parent: AppBundle\Repository\BaseDoctrineRepository
# overrides the first argument (using the special index_N key)
arguments:
index_0: '@doctrine.custom_entity_manager'
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<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://symfony.com/schema/dic/services
http://symfony.com/schema/dic/services/services-1.0.xsd">
<services>
<!-- ... -->
<!-- overrides the public setting of the parent service -->
<service id="AppBundle\Repository\DoctrineUserRepository"
parent="AppBundle\Repository\BaseDoctrineRepository"
public="false"
>
<!-- appends the '@app.username_checker' argument to the parent
argument list -->
<argument type="service" id="app.username_checker" />
</service>
<service id="AppBundle\Repository\DoctrinePostRepository"
parent="AppBundle\Repository\BaseDoctrineRepository"
>
<!-- overrides the first argument (using the index attribute) -->
<argument index="0" type="service" id="doctrine.custom_entity_manager" />
</service>
<!-- ... -->
</services>
</container>
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use AppBundle\Repository\DoctrineUserRepository;
use AppBundle\Repository\DoctrinePostRepository;
use AppBundle\Repository\BaseDoctrineRepository;
use Symfony\Component\DependencyInjection\ChildDefinition;
use Symfony\Component\DependencyInjection\Reference;
// ...
$definition = new ChildDefinition(BaseDoctrineRepository::class);
$definition->setClass(DoctrineUserRepository::class);
// overrides the public setting of the parent service
$definition->setPublic(false);
// appends the '@app.username_checker' argument to the parent argument list
$definition->addArgument(new Reference('app.username_checker'));
$container->setDefinition(DoctrineUserRepository::class, $definition);
$definition = new ChildDefinition(BaseDoctrineRepository::class);
$definition->setClass(DoctrinePostRepository::class);
// overrides the first argument
$definition->replaceArgument(0, new Reference('doctrine.custom_entity_manager'));
$container->setDefinition(DoctrinePostRepository::class, $definition);