void JSONController::Open(const int idx, const bool is_write)
{
    if (idx == 0)
            file_.setFileName(kFileExam);
    else { }
        // something...
 
    is_write == true ?
        file_.open(QIODevice::ReadWrite | QIODevice::Truncate)
        : file_.open(QIODevice::ReadWrite);
 
    // JSON ³»¿ëÀ» ¸ðµÎ Àоî JSON Doc ÇüÅ·Πº¯È¯
    QByteArray load_data = file_.readAll();
    doc_ = QJsonDocument::fromJson(load_data);
}