Need help with serialization of QMaps

Hi,

I try to serialize the member variable QMap <int, QByteArray> in an overloaded operator function, but I get the following compiler errror: no match for 'operator<<' in 'ds << map'

This is my overloaded operator function

Code:

---

QDataStream& operator<<(QDataStream& ds, const NetShmMessage & msg )
{
    QMap<int, QByteArray> map;
    map[1] = QByteArray("one");
    map[2] = QByteArray("two");
 
    ds << map;
    return ds;
}

---

In my main I'm calling

Code:

---

QBuffer tempDevice;
tempDevice.open(QIODevice::WriteOnly);
QDataStream stream(&tempDevice);
stream << msgNet;

---

msgNet is an instance of NetShmMessage wich is holding the map.
If I'm calling stream << map (with previos data definitions) in the main it is working, but not from the overloaded operator. What am I missing?

The overloaded operator is defined as global with friend prefix.

Any help would be really appreciated.

Do you have appropriate includes? QMap, QDataStream..