I want to set the value of a textfield based upon the selection of a field above. You can choose a template and the textfield would have it as a value.

This is the select field used to select the template with the ajax call

// Template Select field $form['template'] = [ '#type' => 'select', '#title' => $this->t('Template'), '#options' => $event_templates_select, '#required' => TRUE, '#ajax' => [     'callback' => '::changeOutputValue',     'disable-refocus' => FALSE,     element.         'event' => 'change',         'wrapper' => 'edit-output',         'progress' =>[             'type' => 'throbber',             'message' => $this->t('Updating e-mail template'),         ],     ] ]; 

This is the textfield that I want to display the value. It’s in a ckeditor.

// Textarea field $form['output'] = [ '#type' => 'text_format', '#format' => 'full_html', '#required' => TRUE, '#disabled' => FALSE, '#value' => 'hallo', '#prefix' => '<div id="edit-output" class="acceptform__output">', '#suffix' => '</div>', ]; 

And finally, the ajax function

  public function changeOutputValue(array &$form, FormStateInterface $form_state) {      $selected_option =  $form_state->getValue('template');     if ($selected_option == 0){         $output_text = '';     } else {         $template = Drupal::entityTypeManager()->getStorage('taxonomy_term')->load($selected_option);         $tempate_content = $template->get('field_template')->getValue();         $tempate_content = $tempate_content[0]['value'];         $output_text = $tempate_content;     }       $form['output']['#value'] = $output_text;      $response = new AjaxResponse();     return $response;    }    } 

Can someone explain what I’m doing wrong. I was trying to follow the drupal 8 form api docs but I can’t get it to work with a ckeditor field.

The select field contains a number of e-mail templates. Upon selecting one, I want to display the template in the output field with a ckeditor so the user can still make changes if necessary.

I’m using Drupal 8 with a custom module.

Thanks in advance.