TestFieldWidgetMultiple.php

<?php

namespace Drupal\field_test\Plugin\Field\FieldWidget;

use Drupal\Core\Field\FieldDefinitionInterface;
use Drupal\Core\Field\FieldItemListInterface;
use Drupal\Core\Field\WidgetBase;
use Drupal\Core\Form\FormStateInterface;
use Symfony\Component\Validator\ConstraintViolationInterface;

/**
 * Plugin implementation of the 'test_field_widget_multiple' widget.
 *
 * The 'field_types' entry is left empty, and is populated through
 * hook_field_widget_info_alter().
 *
 * @see field_test_field_widget_info_alter()
 *
 * @FieldWidget(
 *   id = "test_field_widget_multiple",
 *   label = @Translation("Test widget - multiple"),
 *   multiple_values = TRUE,
 *   weight = 10
 * )
 */
class TestFieldWidgetMultiple extends WidgetBase {
    
    /**
     * {@inheritdoc}
     */
    public static function defaultSettings() {
        return [
            'test_widget_setting_multiple' => 'dummy test string',
        ] + parent::defaultSettings();
    }
    
    /**
     * {@inheritdoc}
     */
    public function settingsForm(array $form, FormStateInterface $form_state) {
        $element['test_widget_setting_multiple'] = [
            '#type' => 'textfield',
            '#title' => t('Field test field widget setting'),
            '#description' => t('A dummy form element to simulate field widget setting.'),
            '#default_value' => $this->getSetting('test_widget_setting_multiple'),
            '#required' => FALSE,
        ];
        return $element;
    }
    
    /**
     * {@inheritdoc}
     */
    public function settingsSummary() {
        $summary = [];
        $summary[] = t('@setting: @value', [
            '@setting' => 'test_widget_setting_multiple',
            '@value' => $this->getSetting('test_widget_setting_multiple'),
        ]);
        return $summary;
    }
    
    /**
     * {@inheritdoc}
     */
    public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state) {
        $values = [];
        foreach ($items as $item) {
            $values[] = $item->value;
        }
        $element += [
            '#type' => 'textfield',
            '#default_value' => implode(', ', $values),
            '#element_validate' => [
                [
                    get_class($this),
                    'multipleValidate',
                ],
            ],
        ];
        return $element;
    }
    
    /**
     * {@inheritdoc}
     */
    public function errorElement(array $element, ConstraintViolationInterface $violation, array $form, FormStateInterface $form_state) {
        return $element;
    }
    
    /**
     * Element validation helper.
     */
    public static function multipleValidate($element, FormStateInterface $form_state) {
        $values = array_map('trim', explode(',', $element['#value']));
        $items = [];
        foreach ($values as $value) {
            $items[] = [
                'value' => $value,
            ];
        }
        $form_state->setValueForElement($element, $items);
    }
    
    /**
     * {@inheritdoc}
     * Used in \Drupal\field\Tests\EntityReference\EntityReferenceAdminTest::testAvailableFormatters().
     */
    public static function isApplicable(FieldDefinitionInterface $field_definition) {
        // Returns FALSE if machine name of the field equals field_onewidgetfield.
        return $field_definition->getName() != "field_onewidgetfield";
    }

}