RouterCategoryField

RouterCategoryField extends Joomla's CategoryField and automatically adjusts its multiple behaviour based on the J2Commerce sef_router component parameter:

• modern router — single category selection only (canonical URLs, Joomla 6 best practice).
• legacy router — multi-select allowed (backward-compatible with J2Store URLs that supported multiple category assignment).

Class Details

Property	Value
Class	RouterCategoryField
Namespace	J2Commerce\Component\J2commerce\Administrator\Field
File	administrator/components/com_j2commerce/src/Field/RouterCategoryField.php
Extends	Joomla\CMS\Form\Field\CategoryField
Field type string	RouterCategory
Since	6.0.8

Router Mode Detection

protected function isMultipleMode(): bool
{
    $params    = ComponentHelper::getParams('com_j2commerce');
    $sefRouter = $params->get('sef_router', 'modern');

    return $sefRouter === 'legacy';
}

isMultipleMode() is called from both __get('multiple') and setup() to ensure the multiple attribute is correctly set before the parent CategoryField builds its rendered output.

XML Usage

<form addfieldprefix="J2Commerce\Component\J2commerce\Administrator\Field">
    <fieldset name="basic">
        <field
            name="catid"
            type="RouterCategory"
            label="JCATEGORY"
            extension="com_content"
            required="true"
        />
    </fieldset>
</form>

XML Attributes

All attributes accepted by Joomla's CategoryField are supported. The multiple attribute is overridden at runtime by isMultipleMode() regardless of any value set in XML.

Attribute	Required	Description
name	Yes	Field name. In legacy mode, submitted as name[].
type	Yes	Must be RouterCategory.
label	Yes	Language key for the field label.
extension	No	Component extension filter, e.g. com_content. Defaults to CategoryField default.
required	No	Marks the field as required.
multiple	Ignored	Overridden by router mode detection.

Behaviour by Router Mode

sef_router value	multiple	Stored value type
modern (default)	false	Single integer category ID
legacy	true	Array of integer category IDs

Usage Notes

• Use RouterCategoryField in product edit forms when the router mode may be switched between installs. It removes the need to maintain two separate form field definitions.
• When migrating a site from legacy to modern router mode, existing multi-value category assignments (arrays) are read back as single values because the field coerces multiple = false — the first array element wins. Ensure data migration strips extra categories before switching modes in production.
• For the advanced use case where you need the modal category picker with create/edit buttons, use RouterModalCategoryField instead.

Related

• RouterModalCategoryField — Delegates to modal_category (modern) or multi-select list (legacy)
• RoutertypeField — Hidden field exposing the active router type for showon conditions