Convert QMap to JSON

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());
}