How can I read QVariantMap send from Pyqt5 ia QDataStream ?

RahibeMeryem

I have QVariant Map in python:

data = {'mq_username': ('123'),  'np_database': ('png') ,  'category': ('png') ,  'enroll_name': ('png') ,  'notes': ('png') ,   'file': ('png') ,
            'np_database': ('png') , 'PNG-image': (png) }
    v = QVariant(data)
    block = QByteArray()
    xout = QDataStream(block, QIODevice.WriteOnly)
    xout.setVersion(qt.QDataStream.Qt_5_10)
    xout << v
    xox = (b'')
    xox = block.data()
    res = client.publish(test_kanali, xox, 2, retain=False)

receving perfectly from mqt in python and can deserialize :

            block = qt.QByteArray(message.payload)
            out = qt.QDataStream(block, qt.QIODevice.ReadOnly)
            out.setVersion(qt.QDataStream.Qt_5_10)

            keys = out.readQVariant()

But I cant figure aout how to do in c++ ?

        QVariantMap vmat_x;

        QDataStream stream(message);
        stream.setVersion(QDataStream::Qt_5_10);
        stream >> vmat_x ;

vmat_x is alway empty ?

Best

JonB

@RahibeMeryem
The problem is really at the Python side, not the C++ side. If you intend to share with C++, you cannot afford to write any Python-object-type into the stream; it looks like you have written a PyQt_PyObject, and that would mean it is only readable by PyQt5.

Christian Ehrlicher

@RahibeMeryem said in How can I read QVariantMap send from Pyqt5 ia QDataStream ?:

vmat_x is alway empty ?

Because you try to read a pointer instead an object.

RahibeMeryem

@Christian-Ehrlicher sorry its not pointer I fixed.

I cant read anything now also.

BC

SGaist

Hi,

IIRC, you have to read it into a QVariant and then you can extract the QVariantMap.

Christian Ehrlicher

@SGaist said in How can I read QVariantMap send from Pyqt5 ia QDataStream ?:

you have to read it into a QVariant and then you can extract the QVariantMap.

You're right - I've overseen that he adds a QVariant, not a QVariantMap.

RahibeMeryem

@Christian-Ehrlicher @SGaist

void MainWindow::mq_message_received(const QByteArray &message, const QMqttTopicName &topic) {

//message is the mqt received from Python created QDatastream

        QDataStream stream(message);
        stream.setVersion(QDataStream::Qt_5_10);
        QVariant vmat_t;
        stream >> vmat_t ;
        
  //Convert to QVariantMap



}

I have nothing in the vmat_t QbyteArray.
Would you mind to show me an example How can I get this stream as finally QVarianMap ?

Best
Thanks

Christian Ehrlicher

@RahibeMeryem said in How can I read QVariantMap send from Pyqt5 ia QDataStream ?:

I have nothing in the vmat_t QbyteArray.

First you should make sure that the data you're sending arrive at your receiver by e.g. output the bytearray you send you you receive

RahibeMeryem

stream >> vmat_t ;

QVariant::load: unknown user type with name PyQt_PyObject.

The error

RahibeMeryem

@Christian-Ehrlicher I have python client that read the same data correctly. SO data is arriving properly and can be read from python client as Qvariantmap.

Problem is at the c++ side

Best

JonB

@RahibeMeryem
The problem is really at the Python side, not the C++ side. If you intend to share with C++, you cannot afford to write any Python-object-type into the stream; it looks like you have written a PyQt_PyObject, and that would mean it is only readable by PyQt5.