Invoke QML method from C++

Question

I want to invoke a method in MyMap from my class MyBacklogg, how do I do this when I don't have the object parameters in that class?

I'm going to receive a string, a QByteArray or a QDataStream in MyBacklogg, depending on which one that works the best, and I want to pass these along to my GUI.

main.cpp:

int main(int argc, char *argv[])
{
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
    QGuiApplication app(argc, argv);

    QQmlApplicationEngine engine;
    engine.load(QUrl(QLatin1String("qrc:/qml/main.qml")));
    if (engine.rootObjects().isEmpty())
        return -1;

    QObject *item = engine.rootObjects().first();
    MyTcpSocket s;
    s.init();
    QObject::connect(item, SIGNAL(sendSignal()), &s, SLOT(doSlot()));

    return app.exec();
}

main.qml:

ApplicationWindow {
    id: appWindow
    visible: true
    height: 600
    width: 800
    title: qsTr("MyApp")
    signal sendSignal()

    RowLayout{
        visible: true
        anchors.fill: parent

        MyMap {
            id: mapview
            function myFunc() {
                //function called from MyBacklogg
            }
            function myOtherFunc() {
                sendSignal()
            }
        }
    }
}

MyBacklogg.cpp:

#include "mybacklogg.h"

MyBacklogg::MyBacklogg(QObject *parent) :
    QObject(parent)
{
}

void MyBacklogg::init()
{
    //initialize
}

void MyBacklogg::doSlot()
{
    //function call from MyMap
}

void MyBacklogg::callMethod()
{
    ??????????????????????????????
    QMetaObject::invokeMethod(object, "myFunc",
        Q_RETURN_ARG(QVariant, returnedValue),
        Q_ARG(QVariant, msg));
    ??????????????????????????????
}

Possible duplicate of call QML function from C++ with another QML object as parameter — derM

dtech dtech · Accepted Answer · 2017-11-30T12:35:29

Did you try initializing MyBacklogg by passing the object pointer to it and preserving it as a class member?

Although if you are calling QML functions from C++, in 99.9% of the cases you are doing it wrong.

The proper solution would be to emit a signal from C++ and install a handler for it on the QML side.

Invoke QML method from C++

1 Answers