How do I pass a node field value as view argument to another entity reference field?

Question

The issue seems simple, but I can't get any documentation for it.

I have a content type with two drop-down fields: field_company which lists taxonomy terms and field_protocol which is referencing a view of entity reference type.

I want to pass the field_company value to field_protocol as view argument, so that when the company is selected, the protocol list is automatically filtered via AJAX. I did add an AJAX callback to refresh the node form with field_company field. I don't knoww how to pass the field value and if this value will filter the view by contextual filter.

Answer 1

The way I thought to update the dropdown of the node field will not work. This should be done in this way:

https://codimth.com/blog/web/drupal/dependent-select-dropdowns-using-ajax-node-addedit-form-drupal-8-9

<?php

use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Url;

/**
 * Implements hook_form_alter().
 */
function MODULENAME_form_alter(&$form, FormStateInterface $form_state, $form_id)
{
  if ($form_id == 'node_article_form' || $form_id == 'node_article_edit_form') {

    //add wrapper to select 2
    $form['field_select2']['#prefix'] = '<div id="select2-wrapper">';
    $form['field_select2']['#suffix'] = '</div>';

    // add ajax to select 1
    $form['field_select1']['widget']['#ajax'] = [
      'callback' => 'callback_field_select1_trigger',
      'wrapper' => 'select2-wrapper',
      'event' => 'change',
      'progress' => [
        'type' => 'throbber',
        'message' => t('Fetching content...'),
      ],
    ];

    //get select 2 options in edit form
    $field_select1_value = $form_state->getValue('field_select1');
    if ($form_id == 'node_article_edit_form' && !$field_select1_value) {
      $field_select1_edit_value = isset($form['field_select1']['widget']['#default_value'][0]) ? $form['field_select1']['widget']['#default_value'][0] : null;
      $form['field_select2']['widget']['#options'] = getSelect2Options($field_select1_edit_value);
    }

  }
}

/**
 * @param array $form
 * @param $form_state
 * @return mixed
 */
function callback_field_select1_trigger(array $form, $form_state)
{
  $field_select1_value = $form_state->getValue('field_select1');
  if (!empty($field_select1_value)) {
    $select1_value = $field_select1_value[0]['target_id'];
    $form['field_select2']['widget']['#options'] = getSelect2Options($select1_value);
  } else {
    $form['field_select2']['widget']['#options'] = getAllSelect2Options();
  }
  return $form['field_select2'];
}


/**
 * @param $select1_value
 * @return array
 */
function getSelect2Options($select1_value)
{
  $query = \Drupal::entityQuery('taxonomy_term');
  $query->condition('vid', "select2_term");
  $query->condition('field_select1.0.target_id', $select1_value);
  $tids = $query->execute();
  $terms = \Drupal\taxonomy\Entity\Term::loadMultiple($tids);
  $options = [];
  $options['_none'] = t('- Any -');
  foreach ($terms as $key => $term) {
    $options[$key] = $term->name->value;
  }
  return $options;
}


/**
 * @return array
 */
function getAllSelect2Options()
{
  $query = \Drupal::entityQuery('taxonomy_term');
  $query->condition('vid', "select2_term");
  $tids = $query->execute();
  $terms = \Drupal\taxonomy\Entity\Term::loadMultiple($tids);
  $options = [];
  $options['_none'] = t('- Any -');
  foreach ($terms as $key => $term) {
    $options[$key] = $term->name->value;
  }
  return $options;
}

// example how to get options if select 1 is multiple field
$selectedItems = [];
$default_values = $form['field_select1']['widget']['#default_value'];
if ($default_values != NULL) {
  foreach ($default_values as $key => $value) {
    if ($value != 0) {
      $selectedItems[$value] = $value;
    }
  }
}
if (count($tab) > 0) {
  $form['field_select2']['widget']['#options'] = getSelect2Options($selectedItems);
} else {
  $form['field_select2']['widget']['#options'] = getAllSelect2Options();
}