Doubt about QLabel * usage.

[chobin]

Hi everyone,

I am developing a program which creates dynamically labels and saves their handles in a QList.

The labels are created OnMouse click and are destroyed OnMouse double click.

Actually the program runs without problems, but I wonder if I am doing a correct usage of pointers in order to prevent runtime errors: I would like to know if the memory correspondent to the created label pointers will exists till mouseDoubleClick_slot is called.

Here below an extract of my code.

QList<QLabel*> *tipList;  // declared in the .h file
 
void CommandWindow::mouseRelease_slot(QMouseEvent* e)
{
	QLabel *tip = new QLabel(ui->customPlot);
	tipList->append(tip);
 
        // ...
}
 
void CommandWindow::mouseDoubleClick_slot(QMouseEvent* e)
{
    if (tipList->size())
    {
        for(int i=0; i<(tipList->size()); i++)
        {
           QLabel *tipTmp = tipList->at(i);
           delete tipTmp;
        }
        tipList->clear();
    }
}

QList<QLabel*> *tipList;  // declared in the .h file

void CommandWindow::mouseRelease_slot(QMouseEvent* e)
{
	QLabel *tip = new QLabel(ui->customPlot);
	tipList->append(tip);
    
        // ...
}

void CommandWindow::mouseDoubleClick_slot(QMouseEvent* e)
{
    if (tipList->size())
    {
        for(int i=0; i<(tipList->size()); i++)
        {
           QLabel *tipTmp = tipList->at(i);
           delete tipTmp;
        }
        tipList->clear();
    }
}

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[wysota]

Yes, it will exist.

A simpler alternative to your mouse double click event is:

{
  qDeleteAll(tipList);
  tipList->clear();
}

{
  qDeleteAll(tipList);
  tipList->clear();
}

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By the way, keeping the list itself as a pointer usually does not make sense.

[chobin]

Hi Wysota,

Thanks for your answer. I have followed you suggestion, I have replaced the * QList declaration with a QList.

My program seems to run as expected.