Service Method Calls and Setter Injection

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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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namespace AppBundle\Service;

use Psr\Log\LoggerInterface;

class MessageGenerator
{
    private $logger;

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

    // ...
}

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

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# app/config/services.yml
services:
    app.message_generator:
        # ...
        calls:
            - method: setLogger
              arguments:
                  - '@logger'
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