如何从另一个Qt小部件窗体类调用MainWindow类

class MainWindow : public QMainWindow
{
    Q_OBJECT

signals:
    void callFunction();
};

class Widget : public QWidget
{
    Q_OBJECT

public slots:
    void onCallFunction()
    {
        MainWindow* mainWindow = qobject_cast<MainWindow*>(parent());
        if (mainWindow)
        {
            // 调用MainWindow类中的功能
            mainWindow->someFunction();
        }
    }
};

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    Widget* widget = new Widget(this);
    connect(this, &MainWindow::callFunction, widget, &Widget::onCallFunction);
}

void Widget::onButtonClicked()
{
    emit callFunction();
}