How to call a slot on quit

Question

I want to update my database just before my Qt application closes.

I want something like connect(this, SIGNAL(quit()), this, SLOT(updateDatabase())) One way could be to introduce a quit button, but is it possible to achieve this functionality if user presses Alt+F4?

Answer 1

Use signal aboutToQuit() instead.

This signal is emitted when the application is about to quit the main event loop, e.g. when the event loop level drops to zero. This may happen either after a call to quit() from inside the application or when the users shuts down the entire desktop session.

The signal is particularly useful if your application has to do some last-second cleanup. Note that no user interaction is possible in this state.

For example :

connect(this, SIGNAL(aboutToQuit()), this, SLOT(updateDatabase()));

Answer 2

There is another way to do it, not aboutToQuit() signal, but to re-implement the closeEvent(QCloseEvent *event). You can call you slot before the statement event->accept();

like this:

void MainWindow::closeEvent(QCloseEvent *event)
{
    call_your_slot_here();
    // accept close event
    event->accept();
}