Service Closures
This feature wraps the injected service into a closure allowing it to be lazily loaded when and if needed. This is useful if the service being injected is a bit heavy to instantiate or is used only in certain cases. The service is instantiated the first time the closure is called, while all subsequent calls return the same instance, unless the service is not shared:
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// src/Service/MyService.php
namespace App\Service;
use Symfony\Component\Mailer\MailerInterface;
class MyService
{
/**
* @param callable(): MailerInterface
*/
public function __construct(
private \Closure $mailer,
) {
}
public function doSomething(): void
{
// ...
$this->getMailer()->send($email);
}
private function getMailer(): MailerInterface
{
return ($this->mailer)();
}
}To define a service closure and inject it to another service, create an
argument of type service_closure:
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# config/services.yaml
services:
App\Service\MyService:
arguments: [!service_closure '@mailer']
# In case the dependency is optional
# arguments: [!service_closure '@?mailer']See also
Service closures can be injected by using autowiring and its dedicated attributes.
See also
Another way to inject services lazily is via a service locator.
Using a Service Closure in a Compiler Pass
In compiler passes you can create a service closure by wrapping the service reference into an instance of ServiceClosureArgument:
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use Symfony\Component\DependencyInjection\Argument\ServiceClosureArgument;
use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\DependencyInjection\Reference;
public function process(ContainerBuilder $container): void
{
// ...
$myService->addArgument(new ServiceClosureArgument(new Reference('mailer')));
}
