ConfigFormBase.php

<?php

namespace Drupal\Core\Form;

use Drupal\Core\Config\ConfigFactoryInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;

/**
 * Base class for implementing system configuration forms.
 */
abstract class ConfigFormBase extends FormBase {
  use ConfigFormBaseTrait;
  
  /**
   * Constructs a \Drupal\system\ConfigFormBase object.
   *
   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
   *   The factory for configuration objects.
   */
  public function __construct(ConfigFactoryInterface $config_factory) {
    $this->setConfigFactory($config_factory);
  }
  
  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    return new static($container->get('config.factory'));
  }
  
  /**
   * {@inheritdoc}
   */
  public function buildForm(array $form, FormStateInterface $form_state) {
    $form['actions']['#type'] = 'actions';
    $form['actions']['submit'] = [
      '#type' => 'submit',
      '#value' => $this->t('Save configuration'),
      '#button_type' => 'primary',
    ];
    // By default, render the form using system-config-form.html.twig.
    $form['#theme'] = 'system_config_form';
    return $form;
  }
  
  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) {
    $this->messenger()
      ->addStatus($this->t('The configuration options have been saved.'));
  }

}