Calling JS functions in loaded components from C++

[Alper]

Hi
i have main.qml file that it have one JS function in it, i can call the function from C++ by "Q_INVOKABLE" and "QMetaObject::invokeMethod", also i have another Qml file "MyFile.qml" that loaded into "main.qml" with this code:

            var component = Qt.createComponent("file:MyFile.qml");
            var object  = component.createObject(container, {"x": 0, "y": 0});

i cant call functions in MyFile.qml from C++.

auto root_object = engine->rootObj().first();
QMetaObject::invokeMethod(rootObj,"jsFunc",Q_RETURN_ARG(QVariant,retVal),Q_ARG(QVariant,conObj));

Error: QMetaObject::invokeMethod: No such method QQuickWindowQmlImpl_QML_35::jsFunc(QVariant)

pls help

Thanks in advance

[A Former User]

@Alper said:

auto root_object = engine->rootObj().first();
QMetaObject::invokeMethod(rootObj,"jsFunc",Q_RETURN_ARG(QVariant,retVal),Q_ARG(QVariant,conObj));

You're trying to call a function named "jsFunc" that is part of root_object (e.g. your ApplicationWindow) but what you want to do is calling a function of an object that is a child of root_object.

So first, you need to find the child in the hierarchy and then you can call one of its functions. The easiest way to find children is by giving them a unique objectName in QML, like:

var object  = component.createObject(mainWindow, {"objectName":"someIdentifier"} );

Then, in C++, you can do this:

QQuickItem *someItem = m_engine->rootObjects().first()->findChild<QQuickItem*>("someIdentifier");
QMetaObject::invokeMethod(someItem,"jsFunc");

[Alper]

@Wieland said:

mainWindow

Thanks for your answer.
So i wrote exactly:

var object  = component.createObject(container, {"objectName":"someIdentifier"} );

and in C++ i did exactly: (it is after loading component into main window)

QQuickItem *someItem = m_engine->rootObjects().first()->findChild<QQuickItem*>("someIdentifier");
QMetaObject::invokeMethod(someItem,"jsFunc");

but it not works.
Have i replace another thing instead of "objectName" or "someIdentifier" ??

[p3c0]

Hi @Alper
Have you made sure that the exact object is found ?
What does qDebug() << someItem print ? It should print the objectName someIdentifier with some other properties.

[Alper]

@Wieland
i solved it!
i just added a line in MyFile.qml like this:

Item {
    objectName: "comId"
...

main .qml:

var object  = component.createObject(scr, {"comId":"someId"} );

C++ side:

  QObject *someItem = m_engine->rootObjects().first()->findChild<QObject*>("comId");
  QMetaObject::invokeMethod(someItem,"jsFunc");

Thanks for your help.

[p3c0]

@Alper Good :)
But following line doesnot make any sense:
var object = component.createObject(scr, {"comId":"someId"} );

You are trying to assign someId to a property named comId which is not present.
The fact that it worked was due to objectName: "comId" in MyFile.qml which was actually referred when you called findChild.

[Alper]

@p3c0

yes thank you
it works with:
var object = component.createObject(scr);
so can i set dynamic objectName property to component?

this worked:

var object  = component.createObject(scr,{"objectName": "newName"});

[p3c0]

@Alper

so can i set dynamic objectName property to component?

Yes. @Wieland's suggestion was correct.
It seems that you passed the wrong parent earlier.