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.