Joomla 4 - how to set namespace for custom field addfieldprefix

Question

I have the editors-xtd\vimeo plugin with this structure

..\plugins\editors-xtd\vimeo\models\fields\(a bunch of custom fields)
..\plugins\editors-xtd\vimeo\forms\form.xml
..\plugins\editors-xtd\vimeo\forms\extra.xml

In both the .xml files I used

<fieldset addfieldpath="/plugins/editors-xtd/vimeo/models/fields">

All working perfect in Joomla 3.9.5+ but I don't know how to set the addfieldprefix in Joomla 4, already tried (according to the JAB presentation) to

<fieldset name="vimeo-options" addfieldprefix="Plugin\EditorsXtd\Vimeo">

In a previous question, I found out how to use com_ajax to set a custom layout for the plugin, here is how I load the .xml files in my layout

..\plugins\editors-xtd\vimeo\tmpl\default.php

via

Form::addFormPath(JPATH_ROOT.'/plugins/editors-xtd/vimeo/forms/');
$form = Form::getInstance('form',JPATH_ROOT.'/plugins/editors-xtd/vimeo/forms/form.xml');
$form->addFieldPath(JPATH_ROOT.'/plugins/editors-xtd/vimeo/models/fields/');
$form->loadFile('extra',false,false);

The pop-up content is empty, no fields loaded from extra.xml.

Thanks for any input/suggestion.

Answer 1

To implement Joomla standard namespacing in a plugin, follow these steps:

First, declare extension's namespace in manifest file:

<namespace>Joomla\Plugin\EditorsXtd\Vimeo</namespace>

If you are editing files on site, you need to delete libraries/autoload_ps4.php file so it can regenerated. If you update the plugin using extension manager, this should be done automatically.

Fields must be placed in plugin's Field directory. So move the contents of plugins/editors-xtd/vimeo/models/fields to plugins/editors-xtd/vimeo/Field.

Field classes and filenames consist of field type and Field suffix. Field type must start with an uppercase and is case sensitive. The filename would be plugins/editors-xtd/vimeo/Field/ExampleField.php and the class name ExampleField. $type property should not contain suffix. You must also add namespace delcaration. An example of field looks like this:

namespace Joomla\Plugin\EditorsXtd\Vimeo\Field;

defined('JPATH_BASE') or die;

use Joomla\CMS\Form\Field\ListField;

class ExampleField extends ListField
{
    protected $type = 'Example';
}

To register fields use addfieldprefix="Joomla\Plugin\EditorsXtd\Vimeo\Field in form.

In form field type should not have a suffix:

<field
    name="whatever"
    type="Example"
/>

If you use camelcase for files/classes, the type in form must be case correctly, e.g. if filename is MyExampleField, the type in form should be MyExample because Myexample or myexample will not be detected.