converting QList<QUuid> to QJsonArray

mzimmers

Hi all -

I need to convert a list of QUuids into a QJsonArray for insertion into a QJsonObject. Here's what I've tried:

typedef QList<QUuid> equipmentUuidList;
QJsonValue qjv;
QJsonArray qja;
equipmentUuidList list;

for (auto &e: list) {
	QVariant qv = QVariant::fromValue(e);
	qjv = qv.toJsonValue(); // this line isn't working.
	qja.append(qjv);
}

but the qjv is assigned Null. Can someone see what I'm doing wrong?

Thanks...

Paul Colby

Hi @mzimmers,

The problem is that the qv metatype is QUuid, but the QVariant::toJsonValue() docs say:

Returns the variant as a QJsonValue if the variant has userType() QJsonValue; otherwise returns a default constructed QJsonValue.

So, for example:

    typedef QList<QUuid> equipmentUuidList;
    QJsonValue qjv;
    QJsonArray qja;
    const equipmentUuidList list { QUuid::createUuid(), QUuid::createUuid(), QUuid::createUuid() };

    qDebug() << "list:" << list;
    for (auto &e: list) {
        QVariant qv = QVariant::fromValue(e);
        qDebug() << "qv:" << qv.typeName() << qv; ///< Type is QUuid.
        qjv = qv.toJsonValue(); ///< null, because qv is not a JSON type.
        qDebug() << "qjv:" << qjv;
        qja.append(qjv);
    }
    qDebug() << "qja:" << qja;

Outputs:

list: QList(QUuid("{f1642ef0-0c4b-48a1-953f-0278e90b6393}"), QUuid("{eb793ede-712c-44e6-8162-8c52af57c383}"), QUuid("{dfee85fe-c0cb-46eb-9d64-6505ddcbca07}"))
qv: QUuid QVariant(QUuid, QUuid("{f1642ef0-0c4b-48a1-953f-0278e90b6393}"))
qjv: QJsonValue(null)
qv: QUuid QVariant(QUuid, QUuid("{eb793ede-712c-44e6-8162-8c52af57c383}"))
qjv: QJsonValue(null)
qv: QUuid QVariant(QUuid, QUuid("{dfee85fe-c0cb-46eb-9d64-6505ddcbca07}"))
qjv: QJsonValue(null)
qja: QJsonArray([null,null,null])

The JSON standard does not have any UUID type - the only way to represent UUIDs in JSON is via strings (with optional JSON Schemas to enforce a pattern). So just convert the UUID to string directly, like:

    typedef QList<QUuid> equipmentUuidList;
    QJsonArray qja;
    const equipmentUuidList list { QUuid::createUuid(), QUuid::createUuid(), QUuid::createUuid() };

    qDebug() << "list:" << list;
    for (const auto &e: list) {
        qja.append(e.toString());
    }
    qDebug() << "qja:" << qja;

Outputs:

list: QList(QUuid("{02a6b10a-0c52-4208-a4c4-d669b621a3cb}"), QUuid("{367cead7-7229-43cb-8176-b08365e83fc9}"), QUuid("{3117ed2a-f7cc-4563-b4af-4af52947e902}"))
qja: QJsonArray(["{02a6b10a-0c52-4208-a4c4-d669b621a3cb}","{367cead7-7229-43cb-8176-b08365e83fc9}","{3117ed2a-f7cc-4563-b4af-4af52947e902}"])

Cheers.

mzimmers

@Paul-Colby oh, of course...this is what happens when I work too late at night -- I make silly mistakes. Thanks for the help.