RouterModalCategoryField

RouterModalCategoryField is a delegating field that creates and proxies a different underlying Joomla form field depending on the active sef_router component setting:

• modern router — delegates to Joomla\Component\Categories\Administrator\Field\Modal\CategoryField (the Joomla Categories modal picker with create/edit/clear buttons).
• legacy router — delegates to Joomla\CMS\Form\Field\CategoryField with multiple = true and the joomla.form.field.list-fancy-select layout.

Class Details

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

Architecture

The delegate field is stored in $this->delegateField. Both getInput() and getLabel() proxy to $this->delegateField->__get('input') and ->__get('label') respectively.

Dependency Injection for Delegated Fields

Joomla's Form::loadField() normally injects database and user dependencies into field instances. Because delegate fields are created manually (bypassing Form::loadField()), RouterModalCategoryField::injectFieldDependencies() performs this injection explicitly:

protected function injectFieldDependencies(FormField $field): void
{
    if ($field instanceof DatabaseAwareInterface) {
        $field->setDatabase($this->getDatabase());
    }

    if ($field instanceof CurrentUserInterface) {
        $field->setCurrentUser($this->getCurrentUser());
    }
}

Value Migration (Legacy → Modern)

When switching from legacy (array of category IDs) to modern (single ID), the field automatically converts the stored array value to a scalar by taking reset($value):

if (is_array($value)) {
    $value = !empty($value) ? (string) reset($value) : '';
}

XML Usage

<form addfieldprefix="J2Commerce\Component\J2commerce\Administrator\Field">
    <fieldset name="basic">
        <field
            name="catid"
            type="RouterModalCategory"
            label="JGLOBAL_CHOOSE_CATEGORY_LABEL"
            extension="com_content"
            required="false"
        />
    </fieldset>
</form>

XML Attributes

Attribute	Required	Description
name	Yes	Field name. Single string in modern mode; submitted as name[] in legacy mode.
type	Yes	Must be RouterModalCategory.
label	No	Language key forwarded to the delegate field. Defaults to JGLOBAL_CHOOSE_CATEGORY_LABEL.
extension	No	Category extension filter. Defaults to com_content.
required	No	Forwarded to the delegate field.

The multiple attribute is always set by the field itself and must not be specified in XML.

Delegate Field Attributes (Modern Mode)

The modal_category delegate is created with select="true", new="true", edit="true", clear="true" — giving the admin the full modal create/edit/clear experience.

Router Mode Detection

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

    return $sefRouter === 'legacy';
}

Related

• RouterCategoryField — Simpler router-aware category field extending CategoryField directly
• RoutertypeField — Hidden field for showon conditions based on router type