QTreeView remove rows - whats wrong

[Dariusz]

Hey

I'm trying to delete all selected rows - children and so on in qtreeView and I'm getting weird error I don't get sigh...

Code :

    QModelIndexList indexList = selectedIndexes();
    QVector<QStandardItem *> itemList;
    QStandardItemModel *modelPtr = dynamic_cast<QStandardItemModel *>(model());
    for (QModelIndex &index:indexList) {
        itemList.push_back(modelPtr->itemFromIndex(index));
    }
    for (QStandardItem *itm:itemList) {
        if (itm) {
            QModelIndex inx = QModelIndex();
            if (itm->parent()) { //// here is error :- ( itm is d was 0xFFFFFFFFFFFFFFFF. but above if (itm) appear to be valid so whats wrong?
                inx = itm->parent()->index();
            }
            modelPtr->removeRow(itm->row(), inx);
        }
    }

What am I doing here wrong? I'm lost :- (

[Dariusz]

Hey

Got some progress on this, one of errors was due to multiple columns during the function execution. I filtered my QModelIndex loop to check if (index.column()==0) to only take 1 item per row.

That fixed some of issues, but other still remain. weird. Removing child items remain problematic.

[Dariusz]

I'm really lost with this. I know that QModelIndex tend to get invalidated when ever I remove row or do stuff in qtreeview/model. But I don't get why this keeps breaking. Tried another loop. Same issue as before still crashing.

I want to loop over items I previously storred in array or other place. So thats why I stay away from selectionModel() and this answer here > https://forum.qt.io/topic/49836/how-to-inside-a-qtreeview-delete-a-selected-row-and-all-his-children/3

    QModelIndexList indexList = selectedIndexes();
    qSort(indexList.begin(), indexList.end(), qGreater<QModelIndex>());
    QVector<QStandardItem *> itemList;
    QStandardItemModel *modelPtr = dynamic_cast<QStandardItemModel *>(model());
    for (QModelIndex &index:indexList) {
        if (index.column() == 0) {
            itemList.push_back(modelPtr->itemFromIndex(index));
        }
    }
    while(itemList.size()>0){
        modelPtr->removeRow(itemList[0]->row(), itemList[0]->index().parent());
        itemList.remove(0);
    }

Any help would be great.

TIA

[SGaist]

Hi,

What custom data do you have ?
How are you handling it ?
Did you try to run your application through the debugger to see where exactly it crashes ?

[Dariusz]

Hey

I dont have any custom data at all.

I just try to store my selection and then delete the items later. Or something like that. It turned out to be quite a pain to solve as well !

The only think I could think off to fix it is this function : - which feels like a dirty hack!

////itemList - is a QVector<QStandardItem*> I saved early.
    for (auto *item:itemList) {
        selectionModel()->select(QItemSelection(item->index(), item->index()),
                                 QItemSelectionModel::Select | QItemSelectionModel::Rows);
    }

    while (!selectionModel()->selectedIndexes().isEmpty()) {
        auto idx = selectionModel()->selectedIndexes().first();
        model()->removeRow(idx.row(), idx.parent());
    }

[SGaist]

Can you explain exactly what procedure you want to follow in order to delete these rows ?

AFAIK, the link you posted earlier shows the correct way to do it.

[VRonin]

Should be something like this:

bool removedByParent(const QHash<QModelIndex,QSet<int> >& mapper, const QModelIndex& childCheck){
if(!childCheck.isValid()) return false;
if(mapper.value(childCheck.parent()).constains(childCheck.row())) return true;
return removedByParent(childCheck.parent());
};

const QModelIndexList selectedIndexList = selectedIndexes();
QHash<QModelIndex /*parent*/, QSet<int> /*rows*/> > indexMapper;
for(auto& idx : selectedIndexList)
indexMapper[idx.parent()].insert(idx.row);
for(auto i=indexMapper.cbegin();i!=indexMapper.cend();++i){
if(removedByParent(i.key())) continue;
auto sortedRows = i.value().toList();
std::sort(sortedRows.begin(),sortedRows.end(),std::greater<int>());
for(int singleRow : qAsConst(sortedRows))
model->removeRow(singleRow,i.key());
}

[Dariusz]

@SGaist For the moment I use the hacky example I posted early.
"Can you explain exactly what procedure you want to follow in order to delete these rows ?"
I just shift/ctrl click on random items in my treeView and then hit delete button.

@VRonin oh dear humh. I see that but won't the QModelINdex list indexes get invalidated after I remove 1 row?

I also try to deal with items directly because of that. Tricky will need to test ur example looks curious! Thanks for chipping in!

Regards
Dariusz

[VRonin]

@Dariusz said in QTreeView remove rows - whats wrong:

I see that but won't the QModelIndex list indexes get invalidated after I remove 1 row?

It's really implementation specific, since you are using QStandardItemModel you are fine, the indexes will still be valid.
In general, however, you are right and QPersistentModelIndex should be used instead.