QTreeView and QAbstractionModel

[The Storm]

Hi all,

I've managed how to add rows and columns with data in them(its a bit complicated for me) but I can't understand how I can remove rows with all the data in them.
For example first how I can make the TreeView in that way that I can select multiple items/rows and then with clicking on buton to remove only the selected ones. If someone can give me some example and maybe where I can read more about this modelling and TreeView. I readed a lot in doc.trolltech.com but I still can't understand how all thoose things works.

Thanks.

[jpn]

Hi, you can adjust QAbstractItemView::selectionMode to make it possible to select multiple items in a view.

To remove items, you could implement QAbstractItemModel::removeRows() more or less like this:

bool MyModel::removeRows(int row, int count, const QModelIndex &parent)
{
    // a sanity check
    if (row < 0 || count <= 0 || (row + count) > rowCount(parent))
        return false;
 
    // inform model-view frame work about upcoming removal
    beginRemoveRows(QModelIndex(), row, row + count - 1);
 
    // remove corresponding items from the internal data structure in here
 
    // inform model-view frame work about finished removal
    endRemoveRows();
 
    // removal succeed
    return true;
}

bool MyModel::removeRows(int row, int count, const QModelIndex &parent)
{
    // a sanity check
    if (row < 0 || count <= 0 || (row + count) > rowCount(parent))
        return false;

    // inform model-view frame work about upcoming removal
    beginRemoveRows(QModelIndex(), row, row + count - 1);

    // remove corresponding items from the internal data structure in here

    // inform model-view frame work about finished removal
    endRemoveRows();

    // removal succeed
    return true;
}

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Now removing a bunch of selected items is kind of problematic. You cannot just remove them in an arbitrary order from the model because removing a certain item might cause other indices to become invalid. The solution is to remove items in reverse order, from end to beginning.

[The Storm]

Is it needed to make new class, can I just use the Standart model for the construction?

[jpn]

Wait, which model are you using? I thought you already had QAbstractItemModel subclass.

[The Storm]

QAbstractItemModel *pModel = new QStandardItemModel(parent);
This is what I use, I saw it in one example.

[wysota]

So you should be able to retrieve selected rows through QItemSelectionModel of the tree view and remove them from the model.

[jpn]

Oh, you should've mentioned that you're using QStandardItemModel. So forget about reimplementing removeRows() then, QStandardItemModel already implements it. Just call it.

[The Storm]

Can you show me example how can I remove the selected rows?

[wysota]

Call removeRow() on the contents of QItemSelectionModel of the view.

[The Storm]

QTreeView doesn't have member that return QItemSelectionModel.

[jpn]

QTreeView is a QAbstractItemView. See QAbstractItemView::selectionModel().

[The Storm]

Ok is it bug in Qt 4.3.1 on Windows that when I remove row it is removed but its like the others become hidden and when I add new they show up again?

[wysota]

Not likely. Can we see the code you wrote?

[The Storm]

Oh, it was my mistake, I though that I must set the model each time when I change it, because I though that setModel() just copy the pointer but it seems its not like that, now all works fine, thanks a lot.