How to remove rows from QStandardItemModel?

deleted385

In the QTableView of the QCompleter I add all object names with tag when a database is attached. When a new database is attached I want to remove the previous database object names before adding news BUT the current approach doesn't work:

So when I attached reverso.db, I've added all those object names (Table, View, Index, Trigger and Column) and when I attached quran.db those old names from reverso.db remains there. Here's the approach I've tried:

void QueryView::onDbChanged(QList<QString>& list)
{
    QVector<QString> itemsToRemove = {"Table", "View", "Index", "Trigger", "Column"};
    QList<QPair<int, QModelIndex>> tobeRemoved;
    auto model = editor->getCompleterModel();
    qDebug() << "before " << model->rowCount();
    for (int i = 0; i < model->rowCount(); i++) {
        auto index = model->index(i, 1);
        if(itemsToRemove.contains(model->data(index).toString()))
            tobeRemoved.append(QPair<int, QModelIndex>(i, index));
    }
    foreach(auto row, tobeRemoved) model->removeRow(row.first, row.second);
    qDebug() << "after " << model->rowCount();
   ...
 }

How to remove those old object names from the QStandardItemModel, model?

JonB

@Emon-Haque
First of all, you will need that reverse-ordering-removal anyway, so keep that principle.

So far as I can see, you have a QTableView, not a QTreeView. So I assume your model is "flat", not "hierarchical" like a tree? In that case you save up model->index(i, 1), whatever that is, and pass it via model->removeRow(row.first, row.second) as row.second. But bool QAbstractItemModel::removeRow(int row, const QModelIndex &parent = QModelIndex())

Removes the given row from the child items of the parent specified

What are you doing passing any parent? Do you just want to omit that parameter?

JonB

@Emon-Haque said in How to remove rows from QStandardItemModel?:

foreach(auto row, tobeRemoved) model->removeRow(row.first, row.second);

Your row.first() holds the original row numbers from the earlier for (int i ... loop, like 0, 1, 2, .... But as soon as you execute the first model->removeRow(row.first /* this is 0 */, row.second); the next row, which was originally 1, is now 0, so you aren't removing what you think you are (you are leaving some items). Print out the bool return result from model->removeRow(row.first, row.second);, you should see that the higher numbers return false.

deleted385

@JonB, right. It'd be nice if I could pass the model->data() (QVariant) in a remove function.

JonB

@Emon-Haque
Well you can't! The simplest from here is get rid of your foreach(auto row, ..., which visits your rows in ascending row number and so gets the numbering wrong during removals, to for (int i = tobeRemoved.count() - 1; i >= 0; i--), which visits the row numbers in descending order, and should then work correctly? [Or populate itemsToRemove in this reverse order if you prefer.]

deleted385

@JonB, I've replaced the foreach with:

for (int i = tobeRemoved.count() - 1; i >= 0; i--)
    model->removeRow(tobeRemoved[i].first, tobeRemoved[i].second);

but it doesn't remove. From the qDebug output I get:

before  184
after  184

so it actually doesn't remove any row.

JonB

@Emon-Haque
First of all, you will need that reverse-ordering-removal anyway, so keep that principle.

So far as I can see, you have a QTableView, not a QTreeView. So I assume your model is "flat", not "hierarchical" like a tree? In that case you save up model->index(i, 1), whatever that is, and pass it via model->removeRow(row.first, row.second) as row.second. But bool QAbstractItemModel::removeRow(int row, const QModelIndex &parent = QModelIndex())

Removes the given row from the child items of the parent specified

What are you doing passing any parent? Do you just want to omit that parameter?

deleted385

@JonB, in the second for If I do model->removeRow(tobeRemoved[i].second.row()) it works.
Thanks.

deleted385

@JonB, one more thing, hope you wouldn't mind. Do I have to call delete on QStandardItem in each column of those rows I'm removing or the Qt framework takes care of that automatically?

JonB

@Emon-Haque
No, the model took ownership of the items when you added them and is responsible for deleting them when you remove them from the model (via removeRow(), but not if you used takeRow(), see https://www.qtcentre.org/threads/63505-removeRow-or-takeRow-in-QStandardItemModel).