如何在Symfony 4服务中使用renderView和twig模板

Question

I'm creating a Emailer Service in my new Symfony 4 application.

I have tried a million things but no luck. I could only find a few resources on this topic for S4 at the moment. Any help is appreciated.

This what I'm trying to achieve. I understand I have to use different services inside of my Emailer service but no luck.

<?php

namespace App\Mailer;

class Emailer
{

    public function sendWelcome($email): \Swift_Mailer
    {
        $message = (new \Swift_Message('P****** - Welcome In!'))
            ->setFrom('no-reply@p****n.com')
            ->setTo($email)
            ->setBody(
                $this->renderView(
                // templates/emails/registration.html.twig
                    'emails/registration.html.twig',
                    array('name' => $user->getUsername())
                ),
                'text/html'
            )
            ->setCharset('utf-8');

        $mailer->send($message);

        return true;
    }
}

Answer 1

First you need to get your templating service injected into your class (constructor injection) and then you can use it to render template.

In the code you can see it that we type-hint it in constructor so Symfony Dependency injection know what we need. Then we just use it. Same will be with your $mailer service.

<?php

namespace App\Mailer;

use Symfony\Component\Templating\EngineInterface;

class Emailer
{

    /**
     * @var EngineInterface
     */
    private $templating;

    /**
     * TestTwig constructor.
     */
    public function __construct(EngineInterface $templating)
    {
        $this->templating = $templating;
    }

    public function sendWelcome($email): \Swift_Mailer
    {
        $message = (new \Swift_Message('P****** - Welcome In!'))
            ->setFrom('no-reply@p****n.com')
            ->setTo($email)
            ->setBody(
                $this->templating->render(
                // templates/emails/registration.html.twig
                    'emails/registration.html.twig',
                    array('name' => $user->getUsername())
                ),
                'text/html'
            )
            ->setCharset('utf-8');

        $mailer->send($message);

        return true;
    }
}

Answer 2

@miles-m a use statement is not the same as injection. A use statement just makes the class accessible with the class name as an alias. Dependency Injection is a pattern that decouples your classes from each other which facilitates better testing and debugging (you can swap out your injected objects for mock objects etc).

One way to inject the Swift_Mailer would be as a constructor parameter, ie

class Emailer
{
    /** @var \Swift_Mailer $mailer */
    private $mailer;    

    public function __construct(
        EngineInterface $templating,
        \Swift_Mailer $mailer <== mailer will be injected here
    ) : \Swift_Mailer
    {
        //...
        $this->mailer->send($message);
    }
}

class CallingClass
{
    //...
    $emailer = new Emailer(
        //EngineInterface instance
        //\Swift_Mailer instance <== injecting 
    );
    $emailer->sendWelcome('email@example.com');
}

Other questions

1. $mailer->send($message)

   Where is your $mailer instance defined?

2. public function sendWelcome($email): \\Swift_Mailer

   return true;

   Is true a valid instance of Swift_Mailer ?