How to invoke QML methods from C++? - qt

Question

I have my QML file which contains methods. These methods need to be called from C++ by using QMetaObject::invokeMethod().
QML :
// MyItem.qml
import QtQuick 2.0
Item {
function signalBroker(name, value) {
if (name == "volume_radio") {
updateVolume(value);
} else if (name == "mute_radio") {
updateMute();
}
}
}

Answer 1

Not sure why you wanna rely on Javascript but here is the complete code.
sample.pro
QT += qml quick
QT -= gui
SOURCES += main.cpp
RESOURCES += resources.qrc
main.cpp
#include <QCoreApplication>
#include <QQmlEngine>
#include <QQmlComponent>
int main(int argc, char *argv[])
{
QCoreApplication app(argc, argv);
QQmlEngine engine;
QQmlComponent component(&engine, "qrc:/main.qml");
QObject *object = component.create();
QVariant name = "volume_radio";
QVariant value = 24;
QMetaObject::invokeMethod(object, "signalBroker",
Q_ARG(QVariant, name),
Q_ARG(QVariant, value));
delete object;
return app.exec();
}
resources.qrc
<RCC>
<qresource prefix="/">
<file>main.qml</file>
</qresource>
</RCC>
main.qml
import QtQuick 2.0
Item {
function updateVolume(value) {
console.log('Volume from C++ = ' + value)
}
function updateMute() {
console.log('Radio is now mute.')
}
function signalBroker(name, value) {
if (name === 'volume_radio') {
updateVolume(value)
} else if (name === 'mute_radio') {
updateMute()
}
}
}
When I run it I get the following output
qml: Volume from C++ = 24
Please Note: On main.cpp when loading the main.qml file please make sure to provide a full path (or :/main.qml) or a qrc URL or the compiler will not find the QML file you are trying to load.
Your app can be a GUI app or a console app, it does not matter so long as you include the corresponding header files and update your .pro file.