I need to delete objects in mainwindow?

[Arendell]

@MainWindow::~MainWindow()
{
delete ui;
}@

This is default code when I create a project in Qt Creator. It's necessary? I think after close program OS will delete it automatically.

[SGaist]

Hi,

Yes it's necessary, ui is allocated on the heap, so it must be deleted when not used anymore. Otherwise you would have a memory leak.

[Arendell]

OK ui is necessary. How about QWidget object? Let's say it's created in MainWindow. Do I need to delete it on MainWindow's destructor?

@MainWindow::~MainWindow()
{
delete QWidget1; // Need?
delete QWidget2;// Need?
delete QWidget3;// Need?
delete ui;// OK
}@

OK ui is needed to be delete but how I know which object need to be delete?

[KA51O]

All objects that you allocated on the heap and which don't have a QObject parent set have to be deleted by you.

[Arendell]

Hmm, OK.

Thanks
[quote author="KA51O" date="1378967418"]All objects that you allocated on the heap and which don't have a QObject parent set have to be deleted by you.[/quote]

[KA51O]

Just to clarify.
@
MainWindow: public QMainWindow
{
MainWindow(QObject* a_parent);
~MainWindow();

QWidget m_StackWidget;
QWidget* m_HeapWidgetWithParent;
QWidget* m_HeapWidgetWithoutParent;
NoQObjectDerivedClass m_StackNoQObj;
NoQObjectDerivedClass* m_HeapNoQObj;
};

MainWindow::MainWindow(QObject* a_parent)
{
// needs to be deleted by you
m_HeapWidgetWithoutParent = new QWidget();
//doesn't need to be deleted by you
m_HeapWidgetWithParent = new QWidget(this);
// needs to be deleted by you
m_HeapNoQObj = new NoQObjectDerivedClass();
}

MainWindow::~MainWindow()
{
delete m_HeapWidgetWithoutParent;
delete m_HeapNoQObj;
}
@

[Jeroentjehome]

Hi,
If this answered your question, set [SOLVED] in front of your first post! Saves other guys reading it.

[Blizzard365]

Hi,
Do you figure out that? I have the same question. Can you help me with that?

[jsulm]

@Blizzard365 What question?
In C++ you have to free unused memory by yourself.
In Qt you don't have to delete children (widgets for example) which have parents - when parent is deleted the children are deleted automatically. See http://doc.qt.io/qt-5/objecttrees.html

[Blizzard365]

@jsulm thx
I got it, ui is not a QObject. I have mistaken 'ui' as a QObject, and setUpUi(MainWindow) is setting parent for 'ui', which is unappropriate.