Working with configuration form

Using $config in the Context of a Form

You can use configuration forms to see how $config can retrieve user-entered data and update information in the {module}.settings.yml file. Here's the code to declare a $config object within a form, typically found in a PHP settings form file.

The Drupal Core ConfigFactory class is a method for reading and writing configuration data, and it's used to instantiate a Config object based on the contents of a given configuration file. The new Config object can then be used to perform CRUD operations on this data.

Example form definition (located in example/src/Form/exampleSettingsForm.php):

namespace Drupal\example\Form;

use Drupal\Core\Form\ConfigFormBase;
use Drupal\Core\Form\FormStateInterface;

/**
 * Configure example settings for this site.
 */
class ExampleSettingsForm extends ConfigFormBase {

  /** 
   * Config settings.
   *
   * @var string
   */
  const SETTINGS = 'example.settings';

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

  /** 
   * {@inheritdoc}
   */
  protected function getEditableConfigNames() {
    return [
      static::SETTINGS,
    ];
  }

  /** 
   * {@inheritdoc}
   */
  public function buildForm(array $form, FormStateInterface $form_state) {
    $config = $this->config(static::SETTINGS);

    $form['example_thing'] = [
      '#type' => 'textfield',
      '#title' => $this->t('Things'),
      '#default_value' => $config->get('example_thing'),
    ];  

    $form['other_things'] = [
      '#type' => 'textfield',
      '#title' => $this->t('Other things'),
      '#default_value' => $config->get('other_things'),
    ];  

    return parent::buildForm($form, $form_state);
  }

  /** 
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) {
    // Retrieve the configuration.
    $this->configFactory->getEditable(static::SETTINGS)
      // Set the submitted configuration setting.
      ->set('example_thing', $form_state->getValue('example_thing'))
      // You can set multiple configurations at once by making
      // multiple calls to set().
      ->set('other_things', $form_state->getValue('other_things'))
      ->save();

    parent::submitForm($form, $form_state);
  }

}

Routing file (example.routing.yml):

example.settings:
  path: '/admin/config/example/settings'
  defaults:
    _form: '\Drupal\example\Form\ExampleSettingsForm'
    _title: 'example'
  requirements:
    _permission: 'administer site configuration'

Using the Config object, you can simplify handling of data collected from a form. With the code above in your settings form file, you can store form data in {module}.settings.yml.

Any class that extends ConfigFormBase must implement the getEditableConfigNames method and return an array of configuration field names it modifies.