Can't invoke Qt c++ method in QML ListView - c++

Question

I have a list of QObjects acting as a qml model for ListView. I can change their properties alright, but can't invoke any slots or Q_INVOKABLE methods. This is the minimal example for my issue (sad that it's still quite large).
Define a really simple class with a property and an invokable method
// DummyObject.h
class DummyElem : public QObject
{
Q_OBJECT
Q_PROPERTY(QString dummy READ getDummy CONSTANT)
public:
explicit DummyElem(QObject *parent = nullptr);
QString getDummy();
Q_INVOKABLE void notifyStuff();
};
Implement trivial methods of this simple class
// DummyObject.cpp
#include "DummyElem.h"
#include <QDebug>
DummyElem::DummyElem(QObject *parent) : QObject(parent) {}
QString DummyElem::getDummy() {return "lorem";}
void DummyElem::notifyStuff() {qDebug() << "ipsum";}
Start a qml app with the list as a root property. Exactly copy-pasted from a tutorial, the one they called q_incokable methods in.
// main.cpp
#include "DummyElem.h"
int main(int argc, char *argv[])
{
QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
QGuiApplication app(argc, argv);
QList<QObject*> dataList;
dataList.append(new DummyElem);
dataList.append(new DummyElem);
QQmlApplicationEngine engine;
QQmlContext* context = engine.rootContext();
context->setContextProperty("dataModel", QVariant::fromValue(dataList));
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
return app.exec();
}
Describe a qml layout with a ListView and a delegate that will invoke a c++ method when clicked.
// main.qml
import QtQuick 2.7
import QtQuick.Window 2.2
Window {
visible: true
ListView {
anchors.fill: parent
model: dataModel
delegate: Component {
Text {
text: model.dummy
MouseArea {
anchors.fill: parent
onClicked: {model.notifyStuff()}
}
}
}
}
}
The issue is hard to debug as a c++ class model can't be json-strigified, nor can i get its javascript entries(). The error i get is "undefined is not a function" which is cool too.
I tried registering the Qt type in QML, but that didn't do anything either.
I'm using Qt libraries version 5.9.4, but the "minimal qt version required" box in QtCreator is set to "Qt 5.6".

Answer 1

You need to use modelData. I'm not entirely sure why, most probably because of the QVariantList. You can read a bit more on this page.
Window {
visible: true
ListView {
anchors.fill: parent
model: dataModel
delegate: Component {
Text {
text: modelData.dummy
MouseArea {
anchors.fill: parent
onClicked: modelData.notifyStuff();
}
}
}
}
}
Fun fact: this is the error I get on Qt 5.11.3:
TypeError: Property 'notifyStuff' of object QQmlDMObjectData(0x5585fe567650) is not a function
At least a bit more telling than undefined, but still not fully descriptive I'd say.