Question

I’d like to do some house keeping stuff (like writing to a file etc) in a Qt app before the app exits. How can I get to this function (exit or whatever is called) in Qt?

Answer 1

You need to connect a slot with the clean up code to the QCoreApplication::aboutToQuit() signal.

This allows you to delete QObjects with QObject::deleteLater() and the objects will be deleted as you have not yet left the main application event loop.

If you are using a C library that requires a ‘shutdown’ call you can normally do that after the return from QCoreApplication::exec().

Example for both techniques:

int main(int,char**)
{
  QApplication app;
  library_init();
  QWidget window;
  window.show();
  QObject::connect(&app, SIGNAL(aboutToQuit()), &window, SLOT(closing()));
  const int retval = app.exec();
  library_close();
  return retval;
}