Why does my Qt application close when I still have a form open (but hidden)

[MachinTrucChose]

This is what I wanted to do: a MainWindow launcher screen which, from a pushButton click event, goes hidden, shows MainWindow2, then when MainWindow2 is closed, is visible again.

This is what I expected to do:

void MainWindow::on_pushButton_clicked()
{
    MainWindow2 *w = new MainWindow2(this);
    connect(w, SIGNAL(destroyed()), this, SLOT(show()));
    this->hide();
    w->show();
}

void MainWindow::on_pushButton_clicked()
{
    MainWindow2 *w = new MainWindow2(this);
    connect(w, SIGNAL(destroyed()), this, SLOT(show()));
    this->hide();
    w->show();
}

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Alas, closing MainWindow2 actually closes the entire application. I ended up having to override MainWindow2's closingEvent to do this:

void MainWindow2::closeEvent(QCloseEvent *event)
{
    if (this->parentWidget() != 0)
    {
        this->parentWidget()->show();
    }
 
    event->accept();
}

void MainWindow2::closeEvent(QCloseEvent *event)
{
    if (this->parentWidget() != 0)
    {
        this->parentWidget()->show();
    }

    event->accept();
}

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This feels like a hack to me because logically I feel the application should never close as long as I never close the parent. Am I doing this wrong?