Service Method Calls and Setter Injection
Tip
If you're using autowiring, you can use #[Required]
or @required
to
automatically configure method calls.
Usually, you'll want to inject your dependencies via the constructor. But sometimes, especially if a dependency is optional, you may want to use "setter injection". For example:
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// src/Service/MessageGenerator.php
namespace App\Service;
use Psr\Log\LoggerInterface;
class MessageGenerator
{
private $logger;
public function setLogger(LoggerInterface $logger): void
{
$this->logger = $logger;
}
// ...
}
To configure the container to call the setLogger
method, use the calls
key:
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# config/services.yaml
services:
App\Service\MessageGenerator:
# ...
calls:
- setLogger: ['@logger']
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<!-- config/services.xml -->
<?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
https://symfony.com/schema/dic/services/services-1.0.xsd">
<services>
<service id="App\Service\MessageGenerator">
<!-- ... -->
<call method="setLogger">
<argument type="service" id="logger"/>
</call>
</service>
</services>
</container>
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// config/services.php
namespace Symfony\Component\DependencyInjection\Loader\Configurator;
use App\Service\MessageGenerator;
return function(ContainerConfigurator $container) {
// ...
$services->set(MessageGenerator::class)
// In versions earlier to Symfony 5.1 the service() function was called ref()
->call('setLogger', [service('logger')]);
};
To provide immutable services, some classes implement immutable setters. Such setters return a new instance of the configured class instead of mutating the object they were called on:
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// src/Service/MessageGenerator.php
namespace App\Service;
use Psr\Log\LoggerInterface;
class MessageGenerator
{
private $logger;
public function withLogger(LoggerInterface $logger): self
{
$new = clone $this;
$new->logger = $logger;
return $new;
}
// ...
}
Because the method returns a separate cloned instance, configuring such a service means using
the return value of the wither method ($service = $service->withLogger($logger);
).
The configuration to tell the container it should do so would be like:
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# config/services.yaml
services:
App\Service\MessageGenerator:
# ...
calls:
- withLogger: !returns_clone ['@logger']
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<!-- config/services.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://symfony.com/schema/dic/services
https://symfony.com/schema/dic/services/services-1.0.xsd">
<services>
<service id="App\Service\MessageGenerator">
<!-- ... -->
<call method="withLogger" returns-clone="true">
<argument type="service" id="logger"/>
</call>
</service>
</services>
</container>
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// config/services.php
use App\Service\MessageGenerator;
use Symfony\Component\DependencyInjection\Reference;
$container->register(MessageGenerator::class)
->addMethodCall('withLogger', [new Reference('logger')], true);
Tip
If autowire is enabled, you can also use annotations; with the previous example it would be:
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/**
* @required
* @return static
*/
public function withLogger(LoggerInterface $logger)
{
$new = clone $this;
$new->logger = $logger;
return $new;
}
You can also leverage the PHP 8 static
return type instead of the
@return static
annotation. If you don't want a method with a
PHP 8 static
return type and a @required
annotation to behave as
a wither, you can add a @return $this
annotation to disable the
returns clone feature.
5.1
Support for the PHP 8 static
return type was introduced in
Symfony 5.1.