FieldStorageAddForm::submitForm

public FieldStorageAddForm::submitForm(array &$form, FormStateInterface $form_state)

public function submitForm(array &$form, FormStateInterface $form_state) {
  $error = FALSE;
  $values = $form_state->getValues();
  $destinations = array();
  $entity_type = $this->entityManager->getDefinition($this->entityTypeId);

  // Create new field.
  if ($values['new_storage_type']) {
    $field_storage_values = [
      'field_name' => $values['field_name'],
      'entity_type' => $this->entityTypeId,
      'type' => $values['new_storage_type'],
      'translatable' => $values['translatable'],
    ];
    $field_values = [
      'field_name' => $values['field_name'],
      'entity_type' => $this->entityTypeId,
      'bundle' => $this->bundle,
      'label' => $values['label'],
      // Field translatability should be explicitly enabled by the users.
      'translatable' => FALSE,
    ];
    $widget_id = $formatter_id = NULL;

    // Check if we're dealing with a preconfigured field.
    if (strpos($field_storage_values['type'], 'field_ui:') !== FALSE) {
      list(, $field_type, $option_key) = explode(':', $field_storage_values['type'], 3);
      $field_storage_values['type'] = $field_type;

      $field_type_class = $this->fieldTypePluginManager->getDefinition($field_type)['class'];
      $field_options = $field_type_class::getPreconfiguredOptions()[$option_key];

      // Merge in preconfigured field storage options.
      if (isset($field_options['field_storage_config'])) {
        foreach (array('cardinality', 'settings') as $key) {
          if (isset($field_options['field_storage_config'][$key])) {
            $field_storage_values[$key] = $field_options['field_storage_config'][$key];
          }
        }
      }

      // Merge in preconfigured field options.
      if (isset($field_options['field_config'])) {
        foreach (array('required', 'settings') as $key) {
          if (isset($field_options['field_config'][$key])) {
            $field_values[$key] = $field_options['field_config'][$key];
          }
        }
      }

      $widget_id = isset($field_options['entity_form_display']['type']) ? $field_options['entity_form_display']['type'] : NULL;
      $formatter_id = isset($field_options['entity_view_display']['type']) ? $field_options['entity_view_display']['type'] : NULL;
    }

    // Create the field storage and field.
    try {
      $this->entityManager->getStorage('field_storage_config')->create($field_storage_values)->save();
      $field = $this->entityManager->getStorage('field_config')->create($field_values);
      $field->save();

      $this->configureEntityFormDisplay($values['field_name'], $widget_id);
      $this->configureEntityViewDisplay($values['field_name'], $formatter_id);

      // Always show the field settings step, as the cardinality needs to be
      // configured for new fields.
      $route_parameters = array(
        'field_config' => $field->id(),
      ) + FieldUI::getRouteBundleParameter($entity_type, $this->bundle);
      $destinations[] = array('route_name' => "entity.field_config.{$this->entityTypeId}_storage_edit_form", 'route_parameters' => $route_parameters);
      $destinations[] = array('route_name' => "entity.field_config.{$this->entityTypeId}_field_edit_form", 'route_parameters' => $route_parameters);
      $destinations[] = array('route_name' => "entity.{$this->entityTypeId}.field_ui_fields", 'route_parameters' => $route_parameters);

      // Store new field information for any additional submit handlers.
      $form_state->set(['fields_added', '_add_new_field'], $values['field_name']);
    }
    catch (\Exception $e) {
      $error = TRUE;
      drupal_set_message($this->t('There was a problem creating field %label: @message', array('%label' => $values['label'], '@message' => $e->getMessage())), 'error');
    }
  }

  // Re-use existing field.
  if ($values['existing_storage_name']) {
    $field_name = $values['existing_storage_name'];

    try {
      $field = $this->entityManager->getStorage('field_config')->create(array(
        'field_name' => $field_name,
        'entity_type' => $this->entityTypeId,
        'bundle' => $this->bundle,
        'label' => $values['existing_storage_label'],
      ));
      $field->save();

      $this->configureEntityFormDisplay($field_name);
      $this->configureEntityViewDisplay($field_name);

      $route_parameters = array(
        'field_config' => $field->id(),
      ) + FieldUI::getRouteBundleParameter($entity_type, $this->bundle);
      $destinations[] = array('route_name' => "entity.field_config.{$this->entityTypeId}_field_edit_form", 'route_parameters' => $route_parameters);
      $destinations[] = array('route_name' => "entity.{$this->entityTypeId}.field_ui_fields", 'route_parameters' => $route_parameters);

      // Store new field information for any additional submit handlers.
      $form_state->set(['fields_added', '_add_existing_field'], $field_name);
    }
    catch (\Exception $e) {
      $error = TRUE;
      drupal_set_message($this->t('There was a problem creating field %label: @message', array('%label' => $values['label'], '@message' => $e->getMessage())), 'error');
    }
  }

  if ($destinations) {
    $destination = $this->getDestinationArray();
    $destinations[] = $destination['destination'];
    $form_state->setRedirectUrl(FieldUI::getNextDestination($destinations, $form_state));
  }
  elseif (!$error) {
    drupal_set_message($this->t('Your settings have been saved.'));
  }
}