public function getClass(array $data)
    {
        if (!array_key_exists($this->field, $data)) {
            return $this->map[$this->getDefault()];
        }

        $type = $data[$this->field];

        // fallback to default if type not found in map
        if (!isset($this->map[$type])) {
            $type = $this->getDefault();
        }

        return $this->map[$type];
    }