Qt - Clear all widgets from inside a QWidget's layout

Question

I have a QWidget in a dialog. Over the course of the program running, several QCheckBox * objects are added to the layout like this:

Answer 1

You can try this:

    while ( QLayoutItem* item = ui->myWidget->layout()->takeAt( 0 ) )
    {
        Q_ASSERT( ! item->layout() ); // otherwise the layout will leak
        delete item->widget();
        delete item;
    }

Answer 2

The wonderful thing about layouts is that they handle a deletion of a widget automatically. So all you really need is to iterate over the widgets and you're done. Since you want to wipe out all children of a given widget, simply do:

for (auto widget: ui->myWidget::findChildren<QWidget*>
                                            ({}, Qt::FindDirectChildrenOnly))
  delete widget;

No need to worry about layouts at all. This works whether the children were managed by a layout or not.

If you want to be really correct, you would need to ignore the widgets that are child widgets but are stand-alone windows. This would be the case if this was in general-purpose library code:

for (auto widget: ui->myWidget::findChildren<QWidget*>
                                            ({}, Qt::FindDirectChildrenOnly)) 
  if (! widget->windowFlags() & Qt::Window) delete widget;

Alternatively, if you only want to delete the children managed by a given layout and its sublayouts:

void clearWidgets(QLayout * layout) {
   if (! layout)
      return;
   while (auto item = layout->takeAt(0)) {
      delete item->widget();
      clearWidgets(item->layout());
   }
}

Answer 3

Given that you have a widget hierarchy consisting of cascaded layouts containing widgets then you should better go for the following.

Step 1: Delete all widgets

    QList< QWidget* > children;
    do
    {
       children = MYTOPWIDGET->findChildren< QWidget* >();
       if ( children.count() == 0 )
           break;
       delete children.at( 0 );
    }
    while ( true );

Step 2: Delete all layouts

    if ( MYTOPWIDGET->layout() )
    {
        QLayoutItem* p_item;
        while ( ( p_item = MYTOPWIDGET->layout()->takeAt( 0 ) ) != nullptr )
            delete p_item;
        delete MYTOPWIDGET->layout();
    }

After step 2 your MYTOPWIDGET should be clean.