QMainWindow destroying

[ecir.hana]

Hello,

I try to study an example from Qt Docs:

http://qt-project.org/doc/qt-5.0/qtw...ndows-sdi.html

I added a destructor to its QMainWindow:

MainWindow::~MainWindow()
{
    qDebug() << "Hello from Destructor!";
}

MainWindow::~MainWindow()
{
    qDebug() << "Hello from Destructor!";
}

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and I would have expected that it prints out the message when I close the window as there is:

setAttribute(Qt::WA_DeleteOnClose);

setAttribute(Qt::WA_DeleteOnClose);

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But it does not print anything on window close event. It prints out the message number of times (= number of windows) when all of the windows are closed first.

Please, can anyone tell me why is this happening? How to make it print out the message on close event (or in the next loop of event loop)?

[amleto]

Yes, destructor is not the same as close event. If you want the message on close event, then put the message in the close event handler!

[ecir.hana]

I apologize for writing it in a bit confusing way.

When I put the message in overloaded close event handler ("void MainWindow::closeEvent(QCloseEvent *event)") it gets displayed immediately after closing the window. The problem is, when I put the message in destructor instead, it gets displayed first when the whole app quits.

So my question is: why is the destructor not called immediately after I close the window? And how to make it being called after the window is closed?

[ChrisW67]

When you click the [x] button (or equivalent) you are triggering a close event and (maybe) hiding the window. You are not destroying the QMainWindow object hence the destructor is not called. The QMainWindow object is not destroyed until C++ scope rules dictate (stack allocated objects) or operator delete is called (heap allocated objects).

If you use the Qt::WA_DeleteOnClose attribute a heap-allocated QWidget object will be destroyed if the object's closeEvent() accepts the closure. It uses the QObject::deleteLater() call, so the deletion is deferred until the program returns to the Qt event loop. This attribute makes no sense if the QWidget object is stack-based (often the case for the program's main window).