public function valid()
    {
        $isValid = true;

        if (count($this->groupFields)) {
            foreach ($this->groupFields as $group) {
                $fields = $group['fields'];
                foreach ($fields as $field) {
                    $isValid = $field->valid();
                    if (!$isValid) {
                        break;
                    }
                }
            }
        }

        return $isValid;
    }