postoffice-1.0.x-dev/examples/postoffice_form_example/src/Form/TestEmailForm.php

<?php

namespace Drupal\postoffice_form_example\Form;

use Drupal\Core\Form\FormBase;
use Drupal\Core\Form\FormInterface;
use Drupal\Core\Form\FormStateInterface;
use Drupal\postoffice_form_example\Email\TestEmail;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Symfony\Component\Mailer\Exception\ExceptionInterface as MailerExceptionInterface;
use Symfony\Component\Mailer\MailerInterface;

/**
 * Example email form.
 */
class TestEmailForm extends FormBase implements FormInterface {

  /**
   * The mailer service.
   */
  protected MailerInterface $mailer;

  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    return new static($container->get('postoffice.mailer'));
  }

  /**
   * Constructs new email test form.
   */
  public function __construct(MailerInterface $mailer) {
    $this->mailer = $mailer;
  }

  /**
   * {@inheritdoc}
   */
  public function getFormId() {
    return 'custom_mailer_mail_test';
  }

  /**
   * {@inheritdoc}
   */
  public function buildForm(array $form, FormStateInterface $form_state) {
    $form['to'] = [
      '#type' => 'email',
      '#title' => $this->t('To'),
      '#default_value' => $this->currentUser()->getEmail(),
    ];
    $form['name'] = [
      '#type' => 'textfield',
      '#title' => $this->t('Name'),
      '#default_value' => $this->currentUser()->getDisplayName(),
    ];

    $form['actions']['#type'] = 'actions';
    $form['actions']['submit'] = [
      '#type' => 'submit',
      '#value' => $this->t('Send'),
    ];

    return $form;
  }

  /**
   * {@inheritdoc}
   */
  public function validateForm(array &$form, FormStateInterface $form_state) {
  }

  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) {
    $mail = (new TestEmail($form_state->getValue('name'), $this->config('system.site')))
      ->to($form_state->getValue('to'));

    try {
      $this->mailer->send($mail);
      $this->messenger()->addMessage($this->t('Mail sent!'));
    }
    catch (MailerExceptionInterface $e) {
      $this->messenger()->addError($this->t('Failed to send mail: @error', [
        '@error' => $e->getMessage(),
      ]));
    }
  }

}