Service Method Calls and Setter Injection
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Read the updated version of this page for Symfony 7.2 (the current stable version).
Tip
If you're using autowiring, you can use @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']4.3
The immutable-setter injection was introduced in Symfony 4.3.
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;
/**
* @return static
*/
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']