RoleRate.php

<?php
/**
 * @file Contains \Drupal\custom_module\Plugin\Field\FieldType\RoleRate
 */

namespace Drupal\custom_module\Plugin\Field\FieldType;

use Drupal\Core\Field\FieldStorageDefinitionInterface;
use Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\TypedData\DataDefinition;

/**
 * Plugin implementation of the 'RoleRate' field type.
 *
 * @FieldType (
 *   id = "rolerate",
 *   label = @Translation("Entity reference RoleRate"),
 *   description = @Translation("Stores the daily rate of any group role member."),
 *   category = @Translation("Reference"),
 *   default_widget = "entity_reference_autocomplete",
 *   default_formatter = "entity_reference_label",
 *   list_class = "\Drupal\Core\Field\EntityReferenceFieldItemList",
 * )
 */
class RoleRate extends EntityReferenceItem {

  /**
   * {@inheritdoc}
   */
  public static function defaultStorageSettings() {
    return [
        'target_type' => 'group_role',
      ] + parent::defaultStorageSettings();
  }

  /**
   * {@inheritdoc}
   */
  public static function propertyDefinitions(FieldStorageDefinitionInterface $field_definition) {
    $properties = parent::propertyDefinitions($field_definition);

    $properties['role_rate'] = DataDefinition::create('integer')
      ->setLabel($field_definition->getSetting('role_rate_label'))
      ->setRequired(TRUE);

    return $properties;
  }

  /**
   * {@inheritdoc}
   */
  public static function schema(FieldStorageDefinitionInterface $field_definition) {

    $schema = parent::schema($field_definition);

    $schema['columns']['role_rate'] = [
      'type' => 'int',
    ];

    return $schema;
  }

  /**
   * {@inheritdoc}
   */
  public static function defaultFieldSettings() {
    return [
        'role_rate_label' => t('Role rate'),
      ] + parent::defaultFieldSettings();
  }

  /**
   * {@inheritdoc}
   */
  public function fieldSettingsForm(array $form, FormStateInterface $form_state) {
    $elements = parent::fieldSettingsForm($form, $form_state);

    $elements['role_rate_label'] = [
      '#type' => 'textfield',
      '#title' => t('Role rate label'),
      '#default_value' => $this->getSetting('role_rate_label'),
      '#description' => $this->t('Also used as a placeholder in multi-value instances.'),
    ];

    return $elements;
  }

  /**
   * {@inheritdoc}
   */
  public static function getPreconfiguredOptions() {
    // In the base EntityReference class, this is used to populate the
    // list of field-types with options for each destination entity type.
    // Too much work, we'll just make people fill that out later.
    // Also, keeps the field type dropdown from getting too cluttered.
    return [];
  }


}