Convert QMap to JSON - c++

Question

I have a QMap object and I would like to convert it to JSON. I am confused how I would accomplish this.
I read QT documentation saying that I can use QDataStream to convert QMap to JSON, but QDataStream seems to convert files: http://doc.qt.io/qt-4.8/datastreamformat.html
// c++
QMap<QString, int> myMap;

Answer 1

It would be easiest to convert the map to QVariantMap which can automatically be converted to a JSON document:
QMap<QString, int> myMap;
QVariantMap vmap;
QMapIterator<QString, int> i(myMap);
while (i.hasNext()) {
i.next();
vmap.insert(i.key(), i.value());
}
QJsonDocument json = QJsonDocument::fromVariant(vmap);
The same thing can be used to create a QJsonObject if you want, via the QJsonObject::fromVariant() static method. Although for QJsonObject you can skip the conversion to variant map step and simply populate the object manually as you iterate the map:
QMap<QString, int> myMap;
QJsonObject json;
QMapIterator<QString, int> i(myMap);
while (i.hasNext()) {
i.next();
json.insert(i.key(), i.value());
}

Answer 2

If you are using Qt 5.5 or higher you could use QJsonDocument::fromVariant, your map could be converted easily to a QVariantMap. If not, try QJson
For your purpose, you are looking for QMAP serialization, see this link: Serialization Qt. Try to set up the constructor with a QByteArray, something like this:
QByteArray serializeMap(const QMap<QString, int>& map) {
QByteArray buffer;
QDataStream stream(&buffer, QIODevice::WriteOnly);
out << map;
return out;
}
That's, will serialize your map in a QByteArray wich could be easily converted to a QString or std::string.