int main(int argc, char *argv[])
{
   QApplication a(argc, argv);

   QWidget window;
   window.setWindowTitle("test");
   window.show();

   return a.exec();
}

Also, if a widget is created on the heap and you want it deleted when it is closed, the simplest way is to set appropriate attribute:

QWidget* w= new QWidget();
w->setAttribute(Qt::WA_DeleteOnClose); //this will call deleteLater() when widget is closed.
w->show();

so basically if I make a new instance of a class like

' className object = new className;
object->show();

it will be deleted once className is desetroyed

Not exactly: every QWidget destroys its children. The deleteLater trick allows to destroy the top-level widget when the application quits.

' className object = new className;
object->show();

it will be deleted once className is desetroyed

but if i were to, say, make a program in which the widgets are added to the layout in the class constructor, should I use the the splitter technique to destroy all the instances of the class that I made?

All the objects (deriving from QObject) you allocate and add to the layout of a widget will be destroyed when the widget itself is destroyed.

@manny said:

also if I need to delete window, should i just add it to splitter so that when splitter is deleted (it is a local variable) window will subsequently be deleted as well?

If I'm not mistaken, you can rely on QApplication::aboutToQuit() to destroy your widget:

connect( &a, SIGNAL( aboutToQuit() ), window, SLOT( deleteLater() ) );

See the doc for detailed information.

also if I need to delete window, should i just add it to splitter so that when splitter is deleted (it is a local variable) window will subsequently be deleted as well?

So in this case, all he needs is
delete window;

I think so, yes. This reparenting is explaing in the doc (Qt 5.5) or there for Qt 4.8. Look at the `Tips for Using Layouts' section.

So in this case, all he needs is
delete window;

As far as I know, the Layout will not delete objects

The layout won't, but the Window will.

Also if you use window for checkbox
checkbox *box = new checkbox(Window);
It will be owned by window and deleted with it.

A widget put in a layout which is then used in another widget has its parent reassigned. Therefore the QCheckBox will indeed be deleted at the time the Window is. I consider a good practice to set the parent anyway, I don't think it hurts.

As far as I know, the Layout will not delete objects
And since you NEW "window," i do not think it get deleted.
You do not need to new QWidget.
Can just be
QWidget window;
In which case it will be deleted when main ends.
Also if you use window for checkbox
checkbox *box = new checkbox(Window);
It will be owned by window and deleted with it.