Can't add custom field to form

Question

I'm trying to add a custom field to the Event form programmatically.

So far, I've created a new extension and enabled it, with hook_civicrm_buildForm function in a PHP file. The function's being executed as I can get it stop at a breakpoint. I'm using the addEntityRef method to add a new field.

/**
 * Implements hook_civicrm_buildForm()
 * 
 * Adds a field for linking a parent event
 *
 * @param string $formName
 * @param CRM_Event_Form_ManageEvent_EventInfo $form
 * @return void
 */
function myExtension_civicrm_buildForm($formName, &$form) {

  if ($formName == 'CRM_Event_Form_ManageEvent_EventInfo') {

    $form->addEntityRef('my_field', ts('My Field'), [
      'entity' => 'Event',
      'placeholder' => ts('- any -'),
      'select' => ['minimumInputLength' => 0],
    ]);

    $form->buildQuickForm();
  }
}

I've followed other posts by adding a template file named my_field.tpl in my extension's templates directory with the contents:

<tr id="my-field-tr">
  <td>Parent Event:</td>
  <td>{$form.my_field.html}</td>
</tr>
{* Reposition the above block after the Event Type field *}
<script type="text/javascript">
  cj('#my-field-tr').insertAfter('.crm-event-manage-eventinfo-form-block-event_type_id')
</script>

But I am struggling to get the field to appear. TIA

Answer 1

There are multiple ways to do this. One is to use a .extra.tpl which has to have the same path and first part of the name as the original .tpl where you want it to get inserted. If you name it that way the tpl file will get picked up automatically. So in this case the original .tpl that controls that event screen is in templates/CRM/Event/Form/ManageEvent/EventInfo.tpl, so you want to make a file templates/CRM/Event/Form/ManageEvent/EventInfo.extra.tpl

Another way is like in your original question but then you're missing the line from the docs (https://docs.civicrm.org/dev/en/latest/hooks/hook_civicrm_buildForm/) that says

CRM_Core_Region::instance('page-body')->add(array(
  'template' => "{$templatePath}/testfield.tpl"
));

to tell it the path and name of your template file. Otherwise it doesn't know about your .tpl file.