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class DependentDropdown in Examples for Developers 8

Same name and namespace in other branches
  1. 3.x modules/ajax_example/src/Form/DependentDropdown.php \Drupal\ajax_example\Form\DependentDropdown

Re-populate a dropdown based on form state.

Hierarchy

Expanded class hierarchy of DependentDropdown

1 string reference to 'DependentDropdown'
ajax_example.routing.yml in ajax_example/ajax_example.routing.yml
ajax_example/ajax_example.routing.yml

File

ajax_example/src/Form/DependentDropdown.php, line 12

Namespace

Drupal\ajax_example\Form
View source 
class DependentDropdown extends FormBase {

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

  /**
   * {@inheritdoc}
   *
   * The $nojs parameter is specified as a path parameter on the route.
   *
   * @see ajax_example.routing.yml
   */
  public function buildForm(array $form, FormStateInterface $form_state, $nojs = NULL) {

    // Add our CSS and tiny JS to hide things when they should be hidden.
    $form['#attached']['library'][] = 'ajax_example/ajax_example.library';

    // Explanatory text with helpful links.
    $form['info'] = [
      '#markup' => $this
        ->t('<p>Like other examples in this module, this form has a path that
          can be modified with /nojs to simulate its behavior without JavaScript.
        </p><ul>
        <li>@try_it_without_ajax</li>
        <li>@try_it_with_ajax</li>
      </ul>', [
        '@try_it_without_ajax' => Link::createFromRoute($this
          ->t('Try it without AJAX'), 'ajax_example.dependent_dropdown', [
          'nojs' => 'nojs',
        ])
          ->toString(),
        '@try_it_with_ajax' => Link::createFromRoute($this
          ->t('Try it with AJAX'), 'ajax_example.dependent_dropdown')
          ->toString(),
      ]),
    ];

    // Our first dropdown lets us select a family of instruments: String,
    // Woodwind, Brass, or Percussion.
    $instrument_family_options = static::getFirstDropdownOptions();

    // When the AJAX request occurs, this form will be build in order to process
    // form state before the AJAX callback is called. We can use this
    // opportunity to populate the form as we wish based on the changes to the
    // form that caused the AJAX request. If the user caused the AJAX request,
    // then it would have been setting a value for instrument_family_options.
    // So if there's a value in that dropdown before we build it here, we grab
    // it's value to help us build the specific instrument dropdown. Otherwise
    // we can just use the value of the first item as the default value.
    if (empty($form_state
      ->getValue('instrument_family_dropdown'))) {

      // Use a default value.
      $selected_family = key($instrument_family_options);
    }
    else {

      // Get the value if it already exists.
      $selected_family = $form_state
        ->getValue('instrument_family_dropdown');
    }
    $form['instrument_family_fieldset'] = [
      '#type' => 'fieldset',
      '#title' => $this
        ->t('Choose an instrument family'),
    ];
    $form['instrument_family_fieldset']['instrument_family_dropdown'] = [
      '#type' => 'select',
      '#title' => $this
        ->t('Instrument Type'),
      '#options' => $instrument_family_options,
      '#default_value' => $selected_family,
      // Bind an ajax callback to the change event (which is the default for the
      // select form type) of the first dropdown. It will replace the second
      // dropdown when rebuilt.
      '#ajax' => [
        // When 'event' occurs, Drupal will perform an ajax request in the
        // background. Usually the default value is sufficient (eg. change for
        // select elements), but valid values include any jQuery event,
        // most notably 'mousedown', 'blur', and 'submit'.
        'callback' => '::instrumentDropdownCallback',
        'wrapper' => 'instrument-fieldset-container',
      ],
    ];

    // Since we don't know if the user has js or not, we always need to output
    // this element, then hide it with with css if javascript is enabled.
    $form['instrument_family_fieldset']['choose_family'] = [
      '#type' => 'submit',
      '#value' => $this
        ->t('Choose'),
      '#attributes' => [
        'class' => [
          'ajax-example-hide',
          'ajax-example-inline',
        ],
      ],
    ];

    // We are using the path parameter $nojs to signal when to simulate the
    // the user turning off JavaScript. We'll remove all the AJAX elements. This
    // is not required, and is here so that we can demonstrate a graceful
    // fallback without having to turn off JavaScript.
    if ($nojs == 'nojs') {

      // Removing the #ajax element tells the system not to use AJAX.
      unset($form['instrument_family_fieldset']['instrument_family_dropdown']['#ajax']);

      // Removing the ajax-example-hide class from the Choose button ensures
      // that our JavaScript won't hide it.
      unset($form['instrument_family_fieldset']['choose_family']['#attributes']);
    }

    // Since we're managing state for this whole fieldset (both the dropdown
    // and enabling the Submit button), we want to replace the whole thing
    // on AJAX requests. That's why we put it in this container.
    $form['instrument_fieldset_container'] = [
      '#type' => 'container',
      '#attributes' => [
        'id' => 'instrument-fieldset-container',
      ],
    ];

    // Build the instrument field set.
    $form['instrument_fieldset_container']['instrument_fieldset'] = [
      '#type' => 'fieldset',
      '#title' => $this
        ->t('Choose an instrument'),
    ];
    $form['instrument_fieldset_container']['instrument_fieldset']['instrument_dropdown'] = [
      '#type' => 'select',
      '#title' => $instrument_family_options[$selected_family] . ' ' . $this
        ->t('Instruments'),
      // When the form is rebuilt during ajax processing, the $selected_family
      // variable will now have the new value and so the options will change.
      '#options' => static::getSecondDropdownOptions($selected_family),
      '#default_value' => !empty($form_state
        ->getValue('instrument_dropdown')) ? $form_state
        ->getValue('instrument_dropdown') : '',
    ];
    $form['instrument_fieldset_container']['instrument_fieldset']['submit'] = [
      '#type' => 'submit',
      '#value' => $this
        ->t('Submit'),
    ];

    // We might normally use #state to disable the instrument fields based on
    // the instrument family fields. But since the premise is that we don't have
    // JavaScript running, #state won't work either. We have to set up the state
    // of the instrument fieldset here, based on the selected instrument family.
    if ($selected_family == 'none') {
      $form['instrument_fieldset_container']['instrument_fieldset']['instrument_dropdown']['#title'] = $this
        ->t('You must choose an instrument family.');
      $form['instrument_fieldset_container']['instrument_fieldset']['instrument_dropdown']['#disabled'] = TRUE;
      $form['instrument_fieldset_container']['instrument_fieldset']['submit']['#disabled'] = TRUE;
    }
    else {
      $form['instrument_fieldset_container']['instrument_fieldset']['instrument_dropdown']['#disabled'] = FALSE;
      $form['instrument_fieldset_container']['instrument_fieldset']['submit']['#disabled'] = FALSE;
    }
    return $form;
  }

  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) {
    $trigger = (string) $form_state
      ->getTriggeringElement()['#value'];
    switch ($trigger) {
      case 'Submit':

        // Submit: We're done.
        $this
          ->messenger()
          ->addMessage($this
          ->t('Your values have been submitted. Instrument family: @family, Instrument: @instrument', [
          '@family' => $form_state
            ->getValue('instrument_family_dropdown'),
          '@instrument' => $form_state
            ->getValue('instrument_dropdown'),
        ]));
        return;
    }

    // 'Choose' or anything else will cause rebuild of the form and present
    // it again.
    $form_state
      ->setRebuild();
  }

  /**
   * Provide a new dropdown based on the AJAX call.
   *
   * This callback will occur *after* the form has been rebuilt by buildForm().
   * Since that's the case, the form should contain the right values for
   * instrument_dropdown.
   *
   * @param array $form
   *   An associative array containing the structure of the form.
   * @param \Drupal\Core\Form\FormStateInterface $form_state
   *   The current state of the form.
   *
   * @return array
   *   The portion of the render structure that will replace the
   *   instrument-dropdown-replace form element.
   */
  public function instrumentDropdownCallback(array $form, FormStateInterface $form_state) {
    return $form['instrument_fieldset_container'];
  }

  /**
   * Helper function to populate the first dropdown.
   *
   * This would normally be pulling data from the database.
   *
   * @return array
   *   Dropdown options.
   */
  public static function getFirstDropdownOptions() {
    return [
      'none' => 'none',
      'String' => 'String',
      'Woodwind' => 'Woodwind',
      'Brass' => 'Brass',
      'Percussion' => 'Percussion',
    ];
  }

  /**
   * Helper function to populate the second dropdown.
   *
   * This would normally be pulling data from the database.
   *
   * @param string $key
   *   This will determine which set of options is returned.
   *
   * @return array
   *   Dropdown options
   */
  public static function getSecondDropdownOptions($key = '') {
    switch ($key) {
      case 'String':
        $options = [
          'Violin' => 'Violin',
          'Viola' => 'Viola',
          'Cello' => 'Cello',
          'Double Bass' => 'Double Bass',
        ];
        break;
      case 'Woodwind':
        $options = [
          'Flute' => 'Flute',
          'Clarinet' => 'Clarinet',
          'Oboe' => 'Oboe',
          'Bassoon' => 'Bassoon',
        ];
        break;
      case 'Brass':
        $options = [
          'Trumpet' => 'Trumpet',
          'Trombone' => 'Trombone',
          'French Horn' => 'French Horn',
          'Euphonium' => 'Euphonium',
        ];
        break;
      case 'Percussion':
        $options = [
          'Bass Drum' => 'Bass Drum',
          'Timpani' => 'Timpani',
          'Snare Drum' => 'Snare Drum',
          'Tambourine' => 'Tambourine',
        ];
        break;
      default:
        $options = [
          'none' => 'none',
        ];
        break;
    }
    return $options;
  }

}

Members

Namesort descending Modifiers Type Description Overrides
DependencySerializationTrait::$_entityStorages protected property An array of entity type IDs keyed by the property name of their storages.
DependencySerializationTrait::$_serviceIds protected property An array of service IDs keyed by property name used for serialization.
DependencySerializationTrait::__sleep public function 1
DependencySerializationTrait::__wakeup public function 2
DependentDropdown::buildForm public function The $nojs parameter is specified as a path parameter on the route. Overrides FormInterface::buildForm
DependentDropdown::getFirstDropdownOptions public static function Helper function to populate the first dropdown.
DependentDropdown::getFormId public function Returns a unique string identifying the form. Overrides FormInterface::getFormId
DependentDropdown::getSecondDropdownOptions public static function Helper function to populate the second dropdown.
DependentDropdown::instrumentDropdownCallback public function Provide a new dropdown based on the AJAX call.
DependentDropdown::submitForm public function Form submission handler. Overrides FormInterface::submitForm
FormBase::$configFactory protected property The config factory. 1
FormBase::$requestStack protected property The request stack. 1
FormBase::$routeMatch protected property The route match.
FormBase::config protected function Retrieves a configuration object.
FormBase::configFactory protected function Gets the config factory for this form. 1
FormBase::container private function Returns the service container.
FormBase::create public static function Instantiates a new instance of this class. Overrides ContainerInjectionInterface::create 87
FormBase::currentUser protected function Gets the current user.
FormBase::getRequest protected function Gets the request object.
FormBase::getRouteMatch protected function Gets the route match.
FormBase::logger protected function Gets the logger for a specific channel.
FormBase::redirect protected function Returns a redirect response object for the specified route. Overrides UrlGeneratorTrait::redirect
FormBase::resetConfigFactory public function Resets the configuration factory.
FormBase::setConfigFactory public function Sets the config factory for this form.
FormBase::setRequestStack public function Sets the request stack object to use.
FormBase::validateForm public function Form validation handler. Overrides FormInterface::validateForm 62
LinkGeneratorTrait::$linkGenerator protected property The link generator. 1
LinkGeneratorTrait::getLinkGenerator Deprecated protected function Returns the link generator.
LinkGeneratorTrait::l Deprecated protected function Renders a link to a route given a route name and its parameters.
LinkGeneratorTrait::setLinkGenerator Deprecated public function Sets the link generator service.
LoggerChannelTrait::$loggerFactory protected property The logger channel factory service.
LoggerChannelTrait::getLogger protected function Gets the logger for a specific channel.
LoggerChannelTrait::setLoggerFactory public function Injects the logger channel factory.
MessengerTrait::$messenger protected property The messenger. 29
MessengerTrait::messenger public function Gets the messenger. 29
MessengerTrait::setMessenger public function Sets the messenger.
RedirectDestinationTrait::$redirectDestination protected property The redirect destination service. 1
RedirectDestinationTrait::getDestinationArray protected function Prepares a 'destination' URL query parameter for use with \Drupal\Core\Url.
RedirectDestinationTrait::getRedirectDestination protected function Returns the redirect destination service.
RedirectDestinationTrait::setRedirectDestination public function Sets the redirect destination service.
StringTranslationTrait::$stringTranslation protected property The string translation service. 1
StringTranslationTrait::formatPlural protected function Formats a string containing a count of items.
StringTranslationTrait::getNumberOfPlurals protected function Returns the number of plurals supported by a given language.
StringTranslationTrait::getStringTranslation protected function Gets the string translation service.
StringTranslationTrait::setStringTranslation public function Sets the string translation service to use. 2
StringTranslationTrait::t protected function Translates a string to the current language or to a given language.
UrlGeneratorTrait::$urlGenerator protected property The url generator.
UrlGeneratorTrait::getUrlGenerator Deprecated protected function Returns the URL generator service.
UrlGeneratorTrait::setUrlGenerator Deprecated public function Sets the URL generator service.
UrlGeneratorTrait::url Deprecated protected function Generates a URL or path for a specific route based on the given parameters.