Set Field Value in Custom List field that is used inside a extended SubformField Class in Multiple Mode

Question

My brain hurts, I'm using a custom listfield inside a subform in multiple mode, the rendering works as expected (two elements in database > two elements in the form). but i'm not able to set the value (selected) state in the listfield. I have no clue on how to pass the data from my subform (that loops over the linking table items) into the field used inside the subform.

This is what i have currently: Custom Subform Field Class:

class SponsorssubformField extends SubformField
{
    /**
     * The form field type.
     *
     * @var    string
     * @since  1.0.0
     */
    protected $type = 'Sponsorssubform';
    protected $min = 0;

    protected $value;

    protected function loadSubFormData(Form $subForm)
    {
        $linked_sponsors = $this->getLinkedSponsors();

        $value = $linked_sponsors ? (array) $linked_sponsors : [];

        // Simple form, just bind the data and return one row.
        if (!$this->multiple) {
            $subForm->bind($linked_sponsors);

            return [$subForm];
        }

        // Multiple rows possible: Construct array and bind values to their respective forms.
        $forms = [];
        $i = 0;
        foreach ($linked_sponsors as $linked_sponsor) {
            echo '<pre>' . var_export($linked_sponsor, 1) . '</pre>';
            $control  = $this->name . '[' . $this->fieldname . $i . ']';
            $itemForm = Form::getInstance($subForm->getName() . $i, $this->formsource, ['control' => $control]);
            $itemForm->bind($linked_sponsor);
            $forms[] = $itemForm;
            $i++;
        }
        return $forms;
    }

    protected function getLinkedSponsors()
    {
        $parentId = $this->form->getValue('id');

        $db = Factory::getContainer()->get(DatabaseInterface::class);
        $query = $db->getQuery(true);
        $query->select('id, sponsor_id');
        $query->from('#__footballmanager_locations_sponsors');
        $query->where('location_id = ' . $parentId);
        $query->order('ordering, id');
        $db->setQuery($query);

        $sponsors = $db->loadObjectList();

        foreach ($sponsors as $sponsor)
        {
            $sponsor->value = $sponsor->sponsor_id;
        }

        return $sponsors;

    }

Custom ListField Class:

class SponsorsField extends ListField{
    /**
     * The form field type.
     *
     * @var    string
     * @since  1.0.0
     */
    protected $type = 'Sponsors';
    protected $value;

    /**
     * Method to get the field options.
     *
     * @return  array  The field option objects.
     *
     * @since   1.0.0
     */
    protected function getOptions()
    {
        echo '<pre>' . var_export( null, 1) . '</pre>';
        $db = Factory::getContainer()->get(DatabaseInterface::class);
        $query = $db->getQuery(true);
        $query->select('id, title');
        $query->from('#__footballmanager_sponsors');
        $query->order('title ASC');
        $db->setQuery($query);
        $sponsors = $db->loadObjectList();

        foreach ($sponsors as $sponsor)
        {
            $options[] = HTMLHelper::_('select.option', $sponsor->id, $sponsor->title);
        }


        // Merge any additional options in the XML definition.
        $options = array_merge(parent::getOptions(), $options);

        return $options;
    }
}

Options got loaded, the elements (count) in the repeatable subform are correct but how can i set the value of inside the subform field?

the linking table structure is as follows:

CREATE TABLE IF NOT EXISTS `#__footballmanager_locations_sponsors`
(
    `id`           int(11)          NOT NULL AUTO_INCREMENT,
    `location_id`  int(11)          NOT NULL,
    `sponsor_id`   int(11)          NOT NULL,
    `ordering`     int(11)                   DEFAULT 0,

    PRIMARY KEY (`id`),
 ...
);

Answer 1

Again it took too long yesterday, The Subfrom had to hold the fieldname as key to set the value. so the key-value has to be named "sponsor" like the field that should represent it.

protected function getLinkedSponsors()
    {
        $parentId = $this->form->getValue('id');

        $db = Factory::getContainer()->get(DatabaseInterface::class);
        $query = $db->getQuery(true);
        $query->select('id, sponsor_id as sponsor, ordering');
        $query->from('#__footballmanager_locations_sponsors');
        $query->where('location_id = ' . $parentId);
        $query->order('ordering, id');
        $db->setQuery($query);

        return $db->loadObjectList();

    }