How do I autopopulate fields in Drupal 8?

Question

How do I autopopulate fields in a node form in drupal 8?

Basically, what I'm trying to do is create an ajax callback to autopopulate fields based on a call to a 3rd party service.

So I'm using hook_form_alter and a custom validate function, and I'm trying to update form values.

function mymodule_validate($form, FormStateInterface &$form_state) {

  $form_state->setValue('title', [['value' => 'testing 123']]);

  $form_state->setRebuild();

}

But this doesn't update the node title.

What's the correct way to alter values in a node form in an ajax callback?

Answer 1

You can hide the field_teaser_title from the node from (set its widget to hidden) then use hook_entity_presave to update its value. Finally show this field in teaser mode.

Answer 2

I was able to get a basic autopopulation callback working based on this question:

How do I modify a core field to use Ajax and add markup?

use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Ajax\AjaxResponse;
use Drupal\Core\Ajax\ReplaceCommand;

/**
 * Implements hook_form_alter() on behalf of mymodule.module.
 */
function mymodule_form_alter(&$form, FormStateInterface $form_state, $form_id) {

  if ($form_id == 'node_publication_form') {

    $form['title']['widget'][0]['value']['#value'] = 'enter title here';

    $form['import_from_third_party_service_id'] = [
      '#type' => 'textfield',
      '#title' => t('Import from third_party_service Id'),
      '#description' => t('To autopopulate fields from third_party_service, enter the third_party_service ID above in the textfield above and hit the import key below'),
      '#maxlength' => 64,
      '#size' => 8,
      '#weight' => '-10',
    ];

    $form['import_from_third_party_service_submit'] = array(
      '#name' => 'custom',
      '#type' => 'submit',
      '#value' => t('Import'),
      '#weight' => -9,
      '#ajax' => [
        'callback' => 'mymodule_import_ajax_callback',
        'wrapper' => 'import-wrapper',
      ],
    );

    $form['#prefix'] = '<div id="import-wrapper">';
    $form['#suffix'] = '</div>';

  }
}

function mymodule_import_ajax_callback($form, &$form_state) {

  // replace with code to get value from third party service
  $new_title = 'hello world';

  $form['title']['widget'][0]['value']['#value'] = $new_title;

  return $form;
}