QQuickView cannot launch ApplicationWindow

#include <QtWidgets/QApplication>
#include <QtQml>
#include <QtQuick/QQuickView>


int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QQmlEngine engine;
    QQmlComponent component(&engine);
    component.loadUrl(QUrl("qrc:/qml/main.qml"));
    if ( !component.isReady() ) {
        qWarning("%s", qPrintable(component.errorString()));
        return -1;
    }
    QObject *topLevel = component.create();
    QQuickWindow *window = qobject_cast<QQuickWindow *>(topLevel);
    if ( !window ) {
        qWarning("Error: Your root item has to be a Window.");
        return -1;
    }
    window->show();
    return app.exec();
}