How to properly call a function with instance in Symfony 4 - php

Question

I'm trying to send an email with SMTP in Symfony 4 and I have the following function as per the docs.
public function send_smtp(\Swift_Mailer $mailer)
{
$message = (new \Swift_Message('Hello Email'))
->setFrom('send#example.com')
->setTo('MyEmail#gmail.com')
->setBody('test email content');
$mailer->send($message);
}
However, I want to call this function from a different one like
$this->send_smtp();
But it complains about 'No parameters are passed' and
$this->send_smtp(\Swift_Mailer);
also gives the error message
Undefined constant 'Swift_Mailer'
What can be the problem and how could it be solved?

Answer 1

There are a few solutions possible. You can add the parameter with typehinting in your action and then use it to call your function:
/**
* #Route("/something")
*/
public function something(\Swift_Mailer $mailer)
{
$this->send_smtp($mailer);
}
or you can retrieve the service from the container in the send_smtp function:
public function send_smtp()
{
$mailer = $this->get('mailer');
$message = (new \Swift_Message('Hello Email'))
->setFrom('send#example.com')
->setTo('MyEmail#gmail.com')
->setBody('test email content');
$mailer->send($message);
}

Answer 2

Create service e.g.
namespace App\Service\Mailer;
class Mailer
{
private $mailer;
public function __construct(\Swift_Mailer $mailer)
{
$this->mailer = $mailer;
}
public function send_smtp()
{
$message = (new \Swift_Message('Hello Email'))
->setFrom('send#example.com')
->setTo('MyEmail#gmail.com')
->setBody('test email content');
$this->mailer->send($message);
}
}
And now you can inject this service wherever you want (e.g. to your Controller action or in another service) via __construct:
public function __construct(Mailer $mailer)
{
$this->mailer = $mailer;
}
public function someAction()
{
$this->mailer->send_smtp()
}
Or you can inject it via method or via property. You can read more about injections here: https://symfony.com/doc/current/components/dependency_injection.html
P.S. I don't recommend you use container's method get because this method works only for public services, but in Symfony 4 services are private by default.