MultiValueTestItem.php

<?php

namespace Drupal\entity_test_update\Plugin\Field\FieldType;

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

/**
 * Defines the 'multi_value_test' field type.
 *
 * @FieldType(
 *   id = "multi_value_test",
 *   label = @Translation("Multiple values test"),
 *   description = @Translation("Another dummy field type."),
 * )
 */
class MultiValueTestItem extends FieldItemBase {
    
    /**
     * {@inheritdoc}
     */
    public static function propertyDefinitions(FieldStorageDefinitionInterface $field_definition) {
        $properties['value1'] = DataDefinition::create('string')->setLabel(t('First value'));
        $properties['value2'] = DataDefinition::create('string')->setLabel(t('Second value'));
        return $properties;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function schema(FieldStorageDefinitionInterface $field_definition) {
        return [
            'columns' => [
                'value1' => [
                    'type' => 'varchar',
                    'length' => 64,
                ],
                'value2' => [
                    'type' => 'varchar',
                    'length' => 64,
                ],
            ],
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function isEmpty() {
        $item = $this->getValue();
        return empty($item['value1']) && empty($item['value2']);
    }
    
    /**
     * {@inheritdoc}
     */
    public static function mainPropertyName() {
        return 'value1';
    }

}