CategoryDuallistboxField

CategoryDuallistboxField extends DuallistboxField and automatically populates the Available panel with all published Joomla com_content categories. Hierarchy is expressed through em-dash indentation. Use it wherever an admin form must let the user assign multiple Joomla categories to a record.

Class Details

Property	Value
Class	CategoryDuallistboxField
Namespace	J2Commerce\Component\J2commerce\Administrator\Field
File	administrator/components/com_j2commerce/src/Field/CategoryDuallistboxField.php
Extends	Joomla\CMS\Form\Field\ListField
Field type string	CategoryDuallistbox
Since	6.0.7

Assets Loaded

Same as DuallistboxField:

Asset	Type	Path
dual-listbox-script	JavaScript	media/com_j2commerce/js/administrator/dual-listbox.js
dual-listbox-style	CSS	media/com_j2commerce/css/administrator/dual-listbox.css

Data Source

getOptions() queries #__categories filtered to extension = 'com_content' and published = 1, ordered by lft ASC (nested set left position) to preserve natural hierarchy. Each category label is prefixed with — repeated (level - 1) times.

SELECT id AS value, title AS text, level
FROM #__categories
WHERE extension = 'com_content'
  AND published = 1
ORDER BY lft ASC

Category IDs (integers) are used as option values. Selected values are stored and submitted as an array of category ID strings.

XML Usage

<form addfieldprefix="J2Commerce\Component\J2commerce\Administrator\Field">
    <fieldset name="basic">
        <field
            name="product_categories"
            type="CategoryDuallistbox"
            label="COM_J2COMMERCE_FIELD_CATEGORIES"
            description="COM_J2COMMERCE_FIELD_CATEGORIES_DESC"
            size="12"
        />
    </fieldset>
</form>

No <option> children are needed — the field populates itself from the database.

XML Attributes

Attribute	Required	Default	Description
name	Yes	—	Field name. Posted as name[] (array of category IDs).
type	Yes	—	Must be CategoryDuallistbox.
label	Yes	—	Language key for the field label.
description	No	—	Language key for the field tooltip.
class	No	form-select	CSS class for the underlying <select> element.
size	No	10	Visible row count per listbox panel.
disabled	No	false	Disables the widget when true.
readonly	No	false	Sets the widget to read-only when true.
required	No	false	Requires at least one selection when true.

Value Handling

Stored values may be:

• A PHP array of category ID strings.
• A comma-separated string of category IDs ("3,7,12").

Both formats are normalised by processValue() before initialising the JavaScript widget.

Error Handling

If the database query fails, the field enqueues an admin error message using COM_J2COMMERCE_ERROR_LOADING_CATEGORIES and returns only any options defined via XML child elements (typically none).

Related

• DuallistboxField — Base dual listbox field with inline options