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.'));
    }

}