Embedding C++ Objects into QML with Context Properties

According to Qt5 documentation: exposing methods including qt slots all public slots of C++ classes that inherit from QObject, are accessible from QML Here what I did:

C++

class MyClass : public QObject
{ Q_OBJECT
public slots: void doStuffFromQmlSlot() { qDebug() << Q_FUNC_INFO; }
public: MyClass() { qDebug() << Q_FUNC_INFO; }
};

my main.cpp contains:

MyClass myClass;
QQmlEngine engine;
engine.rootContext()->setContextProperty( "myclass", &myClass );
QQmlComponent component( &engine, QUrl::fromLocalFile("qml/qtquick-01/main.qml") );
component.create();

QML

import QtQuick 2.0
Rectangle { width: 360 height: 360 Text { text: qsTr("Hello World") anchors.centerIn: parent } MouseArea { anchors.fill: parent onClicked: { myclass.doStuffFromQmlSlot(); Qt.quit(); } }
}

Actually the QtCreator seems to recognixe the exposed myclass object into the QML as it enables auto-completion of both class name (myclass) and the public slot doStuffFromQmlSlot(). When I run the application I unfortunately got the following error:

ReferenceError: myclass is not defined

Any clue on what I'm doing wrong?

1 Answer

I reused your qml file to start a fresh project in QtCreator.

Please find below the files I used to compile and use the application successfully:

the project file: test.pro

# The .cpp file which was generated for your project. Feel free to hack it.
SOURCES += main.cpp
# Please do not modify the following two lines. Required for deployment.
include(qtquick2applicationviewer/qtquick2applicationviewer.pri)
qtcAddDeployment()
HEADERS += myclass.h

myclass.h:

#include <QObject>
#include <qdebug.h>
class MyClass : public QObject
{ Q_OBJECT
public slots: void doStuffFromQmlSlot() { qDebug() << Q_FUNC_INFO; }
public: MyClass() { qDebug() << Q_FUNC_INFO; }
};

main.cpp:

#include <QtGui/QGuiApplication>
#include "qtquick2applicationviewer.h"
#include <QQmlContext>
#include "myclass.h"
int main(int argc, char *argv[])
{ QGuiApplication app(argc, argv); MyClass myClass; QtQuick2ApplicationViewer viewer; viewer.rootContext()->setContextProperty("myclass", &myClass); viewer.setMainQmlFile(QStringLiteral("qml/main.qml")); viewer.showExpanded(); return app.exec();
}

and qml/main.qml being exactly the snippet provided in your question

if you start the project using QtCreator you'll also have the qtquick2applicationviewer/ folder ready to be used. Then qmake && make && ./test will launch the application. If you click on the text element you'll get:

MyClass::MyClass()
void MyClass::doStuffFromQmlSlot()