datetime_extras-8.x-1.x-dev/src/Plugin/Field/FieldType/TimeOnlyField.php

<?php

namespace Drupal\datetime_extras\Plugin\Field\FieldType;

use Drupal\Core\Field\FieldDefinitionInterface;
use Drupal\Core\Form\FormStateInterface;
use Drupal\datetime\Plugin\Field\FieldType\DateTimeItem;

/**
 * Plugin implementation of the 'time_only_field' field type.
 *
 * @FieldType(
 *   id = "time_only_field",
 *   label = @Translation("Time only field"),
 *   description = @Translation("Allows to store only time."),
 *   default_widget = "time_only_field_default",
 *   default_formatter = "time_only_field_default",
 *   list_class = "\Drupal\datetime\Plugin\Field\FieldType\DateTimeFieldItemList"
 * )
 */
class TimeOnlyField extends DateTimeItem {

  /**
   * Value for the 'datetime_type' setting: store a time.
   */
  const DATETIME_TYPE_TIME = 'time';

  /**
   * {@inheritdoc}
   */
  public function storageSettingsForm(array &$form, FormStateInterface $form_state, $has_data) {
    $element = [];

    $element['datetime_type'] = [
      '#type' => 'select',
      '#title' => t('Date type'),
      '#description' => t('Choose the type of date to create.'),
      '#default_value' => $this->getSetting('datetime_type'),
      '#options' => [
        static::DATETIME_TYPE_TIME => t('Time only'),
      ],
      '#disabled' => $has_data,
    ];

    return $element;

  }

  /**
   * {@inheritdoc}
   */
  public static function generateSampleValue(FieldDefinitionInterface $field_definition) {
    // Just pick a date in the past year.
    $timestamp = \Drupal::time()->getRequestTime() - mt_rand(0, 86400 * 365);
    $values['value'] = gmdate(self::DATETIME_STORAGE_FORMAT, $timestamp);
    return $values;
  }

}