如何从 Drupal 8 中的 hook_form_alter 将参数传递给 ajax 回调

Question

我正在尝试实现一个hook_form_alter方法，通过ajax回调在节点的表单显示中修改一个字段的行为。

这个想法是当我从选择列表字段（field_country）中选择一个选项时，修改其他字段列表（field_laws）的值。具体来说，当我选择一个国家时，钩子方法通过ajax回调将此值（当前）传递给changeLawsData。此回调获取一个外部服务，该服务返回一组由先前选择的国家/地区过滤的值。

问题出在回调方法内部，我无法访问包含先前 hook_form_alter 的 $form 和 $form_state 对象。

我的问题是：是否可以通过参数将此对象传递给回调？有了这个，我可以处理表单的状态及其字段，例如。

类似这样的：

    $form['field_country']['widget']['#ajax'] = array(
        'callback' => [$this,'changeLawsData'],
        'event' => 'change',
        'disable-refocus' => FALSE,
        **'arguments' = array($form, $form_state)**
      );

这里是这个实现的完整代码。

<?php

namespace Drupal\obs_urban_system\EventSubscriber;

use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Drupal\hook_event_dispatcher\HookEventDispatcherInterface;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Ajax\AjaxResponse;
use Drupal\Core\Ajax\HtmlCommand;
/**
 * Our event subscriber class.
 */
class NodeUrbanSystemFormAlterEventSubscriber implements EventSubscriberInterface {
    public static function getSubscribedEvents() {
        return [
            HookEventDispatcherInterface::FORM_ALTER => 'hookFormAlter'
        ];
    }

    /**
     * Implements hook_form_alter
     */
    public function hookFormAlter($event) {

        if($event->getFormId() == 'node_urban_system_edit_form') {
            $form = $event->getForm();
            $country = $form['field_country']['widget']['#default_value'];
            $form['field_laws']['widget'][0]['value']['#options'] = \Drupal::service('custom_services.law')->getLawsByContent($country, 'country');
            $form['field_law_articles']['widget'][0]['value']['#options'] = \Drupal::service('custom_services.law')->getLawArticlesByCountry($country);
            $form['field_country']['widget']['#ajax'] = array(
                'callback' => [$this,'changeLawsData'],
                'event' => 'change',
                'disable-refocus' => FALSE
              );
            $event->setForm($form);
        }
    }

    /**
     * @param $form
     * @param \Drupal\Core\Form\FormStateInterface $form_state
     * @return \Drupal\Core\Ajax\AjaxResponse
     */
    function changeLawsData(&$form, FormStateInterface $form_state) {
<!--- HERE IM USING THE $form object --->
        $country = $form['field_country']['widget']['#default_value'];
<!---                                --->
        $laws = \Drupal::service('custom_services.law')->getLawsByContent($country, 'country');

        foreach ($laws as $key => $value) {
            $option .= "<option value='" . $key . "'>" . $value . " </option>";
        }

        $response = new AjaxResponse();
        $response->addCommand(new HtmlCommand('#edit-field-laws-0-value', $option));
        return $response;
    }

}

非常感谢大家。

Answer 1

您需要在 form_alter 中完成所有表单操作。
当 ajax 回调被触发时，表单将被重建并且表单的当前值将在 form_state 中可用。
您的 ajax 回调应该只返回前端需要的内容，它不应该实际操作表单数组。

这是您的代码示例（仅作为示例，未经测试）

<?php

namespace Drupal\obs_urban_system\EventSubscriber;

use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Drupal\hook_event_dispatcher\HookEventDispatcherInterface;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Ajax\AjaxResponse;
use Drupal\Core\Ajax\HtmlCommand;
/**
 * Our event subscriber class.
 */
class NodeUrbanSystemFormAlterEventSubscriber implements EventSubscriberInterface {
    public static function getSubscribedEvents() {
        return [
            HookEventDispatcherInterface::FORM_ALTER => 'hookFormAlter'
        ];
    }

    /**
     * Implements hook_form_alter
     */
    public function hookFormAlter($event) {

        if($event->getFormId() == 'node_urban_system_edit_form') {
            $form = $event->getForm();
            $country = $form['field_country']['widget']['#default_value'];

            // Get the form state object.
            $form_state = $event->getFormState();
            // Here we should check if a country has been selected.
            $country = $form_state->getValue('country');
            if ($country) {
              // populate the options from service here.
              $form['field_laws']['widget']['#options'] = \Drupal::service('custom_services.law')->getLawsByContent($country, 'country');
            } else {
              // Populate with default options.
              $form['field_laws']['widget']['#options'] = [];
            }


            $form['field_law_articles']['widget'][0]['value']['#options'] = \Drupal::service('custom_services.law')->getLawArticlesByCountry($country);
            $form['field_country']['widget']['#ajax'] = array(
                'callback' => [$this,'changeLawsData'],
                'event' => 'change',
                'disable-refocus' => FALSE
              );
            $event->setForm($form);
        }
    }

    /**
     * @param $form
     * @param \Drupal\Core\Form\FormStateInterface $form_state
     * @return \Drupal\Core\Ajax\AjaxResponse
     */
    function changeLawsData(&$form, FormStateInterface $form_state) {
        $response = new AjaxResponse();
        $response->addCommand(new HtmlCommand('#edit-field-laws', $form['field_laws']));
        return $response;
    }

}

请记住以上只是一个例子……