public function updateOptions($modelName)
    {
        $fieldFactory = app('admin_field_factory');
        $response     = array();

        //iterate over the supplied constrained fields
        foreach ($this->request->input('fields', array()) as $field) {
            //get the constraints, the search term, and the currently-selected items
            $constraints   = array_get($field, 'constraints', array());
            $term          = array_get($field, 'term', array());
            $type          = array_get($field, 'type', false);
            $fieldName     = array_get($field, 'field', false);
            $selectedItems = array_get($field, 'selectedItems', false);

            $response[$fieldName] = $fieldFactory->updateRelationshipOptions($fieldName, $type, $constraints, $selectedItems, $term);
        }

        return response()->json($response);
    }