Service Method Calls and Setter Injection

Warning: You are browsing the documentation for Symfony 6.2, which is no longer maintained.

Read the updated version of this page for Symfony 7.2 (the current stable version).

Service Method Calls and Setter Injection

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:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
// src/Service/MessageGenerator.php
namespace App\Service;

use Psr\Log\LoggerInterface;

class MessageGenerator
{
    private LoggerInterface $logger;

    public function setLogger(LoggerInterface $logger): void
    {
        $this->logger = $logger;
    }

    // ...
}

To configure the container to call the setLogger method, use the calls key:

1
2
3
4
5
6
# config/services.yaml
services:
    App\Service\MessageGenerator:
        # ...
        calls:
            - setLogger: ['@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:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
// src/Service/MessageGenerator.php
namespace App\Service;

use Psr\Log\LoggerInterface;

class MessageGenerator
{
    private LoggerInterface $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:

1
2
3
4
5
6
# config/services.yaml
services:
    App\Service\MessageGenerator:
        # ...
        calls:
            - withLogger: !returns_clone ['@logger']

Tip

If autowire is enabled, you can also use attributes; with the previous example it would be:

1
2
3
4
5
6
7
8
#[Required]
public function withLogger(LoggerInterface $logger): static
{
    $new = clone $this;
    $new->logger = $logger;

    return $new;
}

If you don't want a method with a static return type and a #[Required] attribute to behave as a wither, you can add a @return $this annotation to disable the returns clone feature.

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.
TOC
    Version