public function addField($field, $defaults = [])
    {
        // compatibility: for field types
        $class = $this->_default_seed_addField;
        if (is_array($defaults) && isset($defaults['type'])) {
            switch (strtolower($defaults['type'])) {
                case 'boolean':
                    $class = 'Boolean';
                    break;
            }
        }

        $field_object = $this->factory($this->mergeSeeds($defaults, $class), null, '\atk4\data\Field');
        $this->add($field_object, $field);

        return $field_object;
    }