RgbItem.php

<?php

namespace Drupal\field_example\Plugin\Field\FieldType;

use Drupal\Core\Field\FieldItemBase;
use Drupal\Core\Field\FieldStorageDefinitionInterface;
use Drupal\Core\TypedData\DataDefinition;

/**
 * Plugin implementation of the 'field_example_rgb' field type.
 *
 * @FieldType(
 *   id = "field_example_rgb",
 *   label = @Translation("Example Color RGB"),
 *   module = "field_example",
 *   description = @Translation("Demonstrates a field composed of an RGB color."),
 *   default_widget = "field_example_text",
 *   default_formatter = "field_example_simple_text"
 * )
 */
class RgbItem extends FieldItemBase {
    
    /**
     * {@inheritdoc}
     */
    public static function schema(FieldStorageDefinitionInterface $field_definition) {
        return [
            'columns' => [
                'value' => [
                    'type' => 'text',
                    'size' => 'tiny',
                    'not null' => FALSE,
                ],
            ],
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function isEmpty() {
        $value = $this->get('value')
            ->getValue();
        return $value === NULL || $value === '';
    }
    
    /**
     * {@inheritdoc}
     */
    public static function propertyDefinitions(FieldStorageDefinitionInterface $field_definition) {
        $properties['value'] = DataDefinition::create('string')->setLabel(t('Hex value'));
        return $properties;
    }

}