c++ does reads QList<QString> always empty when sent from QML

[shokarta]

hello guys,

I have this:
qml file:

property variant sapSystems:    [{"a": 1, "b": 2, "c": 3},
                                         {"a": 4, "b": 5, "c", 6}]
    Component.onCompleted: {
        var neco = cpp.connectionTest(sapSystems[1]);    // so im sending: {"a": 4, "b": 5, "c", 6}
    }

and in c++ file i have:

void CPP::connectionTest(QList<QString> connParameters)
{
qDebug() << connParameters;    // debugs "QList()"
qDebug() << connParameters.count() << connParameters.size() << connParameters.length();    // debugs: 0 0 0
foreach(auto &x,connParameters)    // debugs 0 as connParameters seems to be empty
    qDebug() << x;
}

howcome on C++ side its empty?

[jsulm]

@shokarta said in c++ does reads QList<QString> always empty when sent from QML:

[{"a": 1, "b": 2, "c": 3},
{"a": 4, "b": 5, "c", 6}]

This is not a list of strings, but a list of objects. So, sapSystems[1] is {"a": 4, "b": 5, "c", 6} which is not a string.

[shokarta]

Right, you totaly right...
but QList<QObject> cant be passed to c++ as wrong conversion...

any idea how to do what im trying to do?

[jsulm]

@shokarta I'm not QML expert, but maybe QList<QVariant>? Or QList<QJsonObject>?

[shokarta]

@jsulm said in c++ does reads QList<QString> always empty when sent from QML:

QList<QJsonObject>

TypeError: Passing incompatible arguments to C++ functions from JavaScript is not allowed.

i dont know how to pass this objects and read it from c++ :(
unless sending JSON string and recreate it to JSON... which to me is very unnecessary bad practice :(
I would realy prefer to send it and read it in any compatibile way

[jsulm]

@shokarta Actually it should be QJsonObject (since {"a": 4, "b": 5, "c", 6} is not a list of objects but an object)

[shokarta]

@jsulm said in c++ does reads QList<QString> always empty when sent from QML:

QJsonObject

but QJsonObject give the very same error:

TypeError: Passing incompatible arguments to C++ functions from JavaScript is not allowed.

[jsulm]

@shokarta Then try QVariant and try to cast to QJsonObject using https://doc.qt.io/qt-6/qvariant.html#toJsonObject

[shokarta]

@jsulm QVariant debugs empty in CPP, so no converion possible :(

[shokarta]

so at the end I converted that object array to JSON in QML, send it to C++, and in CPP recreated to JSON...
bad practice but lets say ifs short code working, probably fast too