Question

in Qt im opening QDialog windows each time i click some item
im doing it with new , i like to be sure im opening only one instance of QDialog for each item
im clicking :

void foo::treeWidget_itemClicked(QTreeWidgetItem *item,nt column)                                               
    .....
    QString groupID = item->data(0, Qt::UserRole).toString();
    QString groupName = item->text(0);
    GroupDialogContainer* pGroupDialogContainer = new GroupDialogContainer(groupID,                                                                               groupName,                                                                                   this);

    pGroupDialogContainer->show();

}

class GroupDialogContainer : public QDialog
{
    Q_OBJECT


public:
    GroupDialogContainer(QString GroupId,QString GroupName,QWidget *parent=0); 
    GroupDialogContainer(QWidget *parent=0);
    virtual ~GroupDialogContainer();
    Ui::GroupDialog ui;

public slots:
    void closeEvent(QCloseEvent *event);
};

do i need to keep some kind of hash or vector of GroupDialogContainer ?
also my second question is :
does each time im closing the QDialog window with close () the object pGroupDialogContainer
that was responsible to open it is destroyer ed ? or do i need to delete it when im detecting that the QDIalog has closed?

Answer 1

Yes, you should probably keep some kind of list of your dialogs to keep track of which ones are already open. If your GroupID is your unique ID then you could do something like this:

QMap DialogMap;

void foo::treeWidget_itemClicked(QTreeWidgetItem *item,nt column)
{
…..
QString groupID = item->data(0, Qt::UserRole).toString();

if (! DialogMap.contains(groupID))
{
  //  Popup the dialog and add it to map
  ...
  DialogMap.insert(groupID, pGroupDialogContainer);
}

}

Now, for the other part. The most important thing is that you need to remove the item from the map when the dialog closes. You could either delete the dialog then, or my suggestion would be to let the dialog delete itself when it closes – as follows:

 // set automatic deletion of object on close
 setAttribute(Qt::WA_DeleteOnClose);

But as I said, you’ll still need to remove the dialog from the Map, or else you’ll have a bad pointer in there, and your code will still think the dialog is open.

So you’ll need some kind of signal from the dialog to indicate that it is closing. There is the finished(int result) signal, that is called when you trigger a result:

This signal is emitted when the
dialog’s result code has been set,
either by the user or by calling
done(), accept(), or reject().

But, you can always create your own signal in your dialog, and emit it when the closeEvent is called in your dialog.

Then in the code that handles the map…

connect( pGroupDialogContainer, SIGNAL(WindowClosed()), this, SLOT(vCleanUpTheMap()));
...
void vCleanUpTheMap()
{
   GroupDialogContainer *pDialog = dynamic_cast<GroupDialogContainer *>(sender());
   if (pDialog)
   {
      // Just to keep things clean disconnect from the dialog.
      disconnect(pDialog);

      //  I am assuming that you can get the key groupID from the dialog
      //  Cause it's a lot easier to remove from a map with the key
      DialogMap.remove(pDialog->GetGroupID());
   }
}

And that’s it.