Symfony 3: How can I inject a service dynamically depending on some runtime variable

Question

let's say I have the following interface/concrete classes:

interface EmailFormatter

class CvEmailFormatter implements EmailFormatter
class RegistrationEmailFormatter implements EmailFormatter
class LostPasswordEmailFormatter implements EmailFormatter

I then have a custom 'mailer' service that's called from my controller actions in order to send an email.

What options do I have for injecting the correct implementation of EmailFormatter to my mailer service depending on the type of email being sent?

Answer 1

I would create a service that picks the right formatter during runtime, either some kind of factory or if your formatters have dependencies maybe a service were you inject the formatters from the container. Something like this:

class MailController extends AbstractController
{
    private $mailer;
    private $mailFormatterSelector;

    public function __construct(...) { ... }

    public function someAction()
    {
        // Do stuff ...

        if (...some condition) {
            $formatter = $this->mailFormatterSelector->getRegisterMailFormatter();
        } else {
            $formatter = $this->mailFormatterSelector->getLostPasswordEmailFormatter();
        }
        $mailer->sendEmail($formatter);

        // Do more stuff ...
    }
}

class MailFormatterSelector()
{
    private $registrationFormatter;

    public function __construct(EmailFormatter $registrationFormatter, ...)
    {
        $this->registrationFormatter = $registrationFormatter;
        ...
    }

    public function getRegisterMailFormatter(): EmailFormatter
    {
        return $this->registrationFormatter;
    }

    // ...
}

Alternatively if you have to pass the formatters into your mailer during construction, you can also create multiple, differently set up instances with different aliases and then inject them as needed into the services and controllers like this:

# config/services.yaml
mailer1:
    class: MyMailler
    arguments:
        $formatter: '@formatter1'
mailer2:
    class: MyMailler
    arguments:
        $formatter: '@formatter2'

MyMailController:
    arguments:
        $mailer: '@mailer2'

In your controller or action you can then pass in mailer1, mailer2, ... (maybe with nicer names) via.