Overloading QDataStream operators

[Uday More]

I am overloading QDataStream operator with my custom class.

#include <QCoreApplication>
#include <QDataStream>
#include<QVector>

class MsgPointAttribute{
public:
    double pointValue;
};

class MsgPoint{
public:
    QVector<MsgPointAttribute> pointAtributes;
    // Additional info like point color can be appended.
};

class MsgPointCloud{
public:
    QString pointType;
    quint32 cloudWidth;
    quint32 cloudHeight;
    quint32 pointsCount;
    QVector<MsgPoint> points;
    // Additional info like cloud properties can be added here can be added here
};

class MsgPointCloudDataResponse{

private :

public:

    quint64 recievedTimestamp;
    QString responseChannelName;
    QString responseDeviceName;
    QString cloudName;
    QVector<MsgPointCloud> pointClouds;


//    friend QDataStream &operator <<(QDataStream &out, const MsgPointCloudDataResponse &other);

};

// you need this if you want to use your type with QVariant
Q_DECLARE_METATYPE(MsgPointCloudDataResponse)

QDataStream &operator <<(QDataStream &out, const MsgPointCloudDataResponse &other){

//    // Register your custom type with Stream operators.
//    qRegisterMetaTypeStreamOperators<qreal>("qreal");

    int pointCloudsCount = other.pointClouds.count();

    // Looping through the list of point clouds.
    for(int i = 0; i < pointCloudsCount; ++i)
    {
        out << other.pointClouds[i].pointType << other.pointClouds[i].cloudWidth <<
               other.pointClouds[i].cloudHeight << other.pointClouds[i].pointsCount;

        int pointCount = other.pointClouds[i].pointsCount;

        for(int j = 0; j < pointCount; ++j)
        {
            int  iPointAttrCount = other.pointClouds[i].points[j].pointAtributes.count();

            for(int k = 0; k < iPointAttrCount; ++k){
                out << other.pointClouds[i].points[j].pointAtributes[k].pointValue;
            }
        }
    }

    return out;
}

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    // Register your custom type with Stream operators.
    qRegisterMetaTypeStreamOperators<MsgPointCloudDataResponse>("MsgPointCloudDataResponse");

    return a.exec();
}

I get the following error and what am I missing.

C:\Qt\Qt5.7.0\5.7\msvc2015_64\include\QtCore/qmetatype.h(777): error C2679: binary '>>': no operator found which takes a right-hand operand of type 'MsgPointCloudDataResponse' (or there is no acceptable conversion)

[J.Hilk]

@Uday-More

I havn't done that myself yet, but it seems like,

qRegisterMetaTypeStreamOperators requieres you to define/overload << as well as >> to also get the data back !?

and you only defined << in the code you showed.

[Uday More]

@J.Hilk Thanks so much. It solved the above problem.
But now eventually i get another error as described below

moc_appcontroller.obj : error LNK2005: "class QDataStream & __cdecl operator<<(class QDataStream &,class MsgPointCloudDataResponse const &)" (??6@YAAEAVQDataStream@@AEAV0@AEBVMsgPointCloudDataResponse@@@Z) already defined in appcontroller.obj
moc_appcontroller.obj : error LNK2005: "class QDataStream & __cdecl operator>>(class QDataStream &,class MsgPointCloudDataResponse &)" (??5@YAAEAVQDataStream@@AEAV0@AEAVMsgPointCloudDataResponse@@@Z) already defined in appcontroller.obj

Note : In appcontroller class I've just used the statement
qRegisterMetaTypeStreamOperators<MsgPointCloudDataResponse>("MsgPointCloudDataResponse");

[VRonin]

Move the implementation of the datastream operators to a .cpp file rather than having it in the header

[Uday More]

@VRonin said in Overloading QDataStream operators:

Move the implementation of the datastream operators to a .cpp file rather than having it in the header

Thanks. This is the solution.

1. Overload both operators
2. Have the overloading code in a cpp file.

[DungeonLords]

In my example I am overloading QDataStream operator with my custom struct.

typedef struct my_struct{
    my_struct(const quint32 my_i, const bool my_b):i{my_i}, b{my_b}{};
    my_struct(){};
    quint32 i{};
    bool b{};
}my_struct_t;

QDataStream &operator<<(QDataStream &out, const my_struct_t& s){
    out << s.i << s.b;
    return out;
}

QDataStream &operator>>(QDataStream &in, my_struct_t& s){
    in >> s.i >> s.b;
    return in;
}