Context property works in QQmlApplicationEngine but not in QQmlEngine.

[adutzu89]

Hello,
Because I cannot save/load position of ApplicationWindow correctly, on X11 I have decided to use QMainWindow as base window application but I am stuck with context properties.
Here you can see how I set the context properties in my main.cpp file.

In the following is how I declared in QMainWindow constructor:

    QQuickWidget *view = new QQuickWidget();
    QQmlEngine *engine = view->engine();
    connect(engine, SIGNAL(quit()), this, SLOT(close()));
    QQmlContext *context = engine->rootContext();
    Util util;
    SettingsController settingsController;
    engine->addImageProvider(QLatin1String("customimage"), new CustomImageProvider());
    engine->addImageProvider(QLatin1String("fontimage"), new FontImageProvider());
    context->setContextProperty("util", &util);
    context->setContextProperty("settingsController", &settingsController);
    context->setContextProperty("applicationPath", "file://" + qApp->applicationDirPath() + "/");
    registerQmlType();
    if (Util::osType() == "android")
        view->setSource(QUrl(QLatin1String("qrc:/main-android.qml")));
    else
        view->setSource(QUrl(QLatin1String("qrc:/main-desktop.qml")));

    if (QFile::exists(QApplication::applicationDirPath() + "/maintenancetool")) {
        QThread thread;
        ThreadWorker *threadWorker = new ThreadWorker();
        threadWorker->moveToThread(&thread);
        QObject::connect(&thread, SIGNAL(finished()), threadWorker, SLOT(deleteLater()));
        QObject::connect(threadWorker, SIGNAL(updateSearchFinished()), &thread, SLOT(quit()));
        thread.start();
        threadWorker->updaterTimerStart();
    }
    view->show();
    view->setResizeMode(QQuickWidget::SizeRootObjectToView);
    view->setClearColor(Qt::transparent);
    setAttribute(Qt::WA_TranslucentBackground);
    loadSettings();
    setCentralWidget(view);
    setMinimumHeight(150);
    setMinimumWidth(140);

My issue is that when I call method of object declared as context property("util" in my example) I get TypeError: Cannot call method '<any-method-here>' of null, while "applicationPath" property works correctly.

Methods are marked as Q_INVOKABLE.

Any ideeas on what am I doing wrong?

[dheerendra]

U r creating stack objects in constructor. All these objects are destroyed once the constructor is over. Create dynamic object & things should work.

[Eeli K]

@adutzu89
@dheerendra is correct. The string works because it's not a pointer or reference but is copied and becomes a javascript string by automatic C++/QML type conversion. However, I don't know what dheerendra means by "dynamic", maybe that they can be heap objects; you can have the objects also as direct members of your main window class without pointers and new. That would be better modern C++ style unless you need to reach the parent main window object from your objects.

[adutzu89]

@dheerendra and @Eeli-K thank you for your answers it helped :).

@Eeli-K he reffers to instantiate the object with the "new" operator.
In my constructor, as an example:

Util *util = new Util();

works correctly.