How to implement removeRow() function for customized model in QT? - c++

Question

I have searched QT doc for reference but I got some questions.
Here is the implementation in QT doc:
bool TableModel::removeRows(int position, int rows, const QModelIndex &index)
{
Q_UNUSED(index);
beginRemoveRows(QModelIndex(), position, position + rows - 1);
for (int row = 0; row < rows; ++row) {
listOfPairs.removeAt(position);
}
endRemoveRows();
return true;
}
I think it uses index.row in the tableview to directly locate the data in the model. But what if I enable sorting for the tableview? After sorting, the index in the tableview doesn't correspond to the data in the model. The first row in the tableview may be the third data in the model.
How can I locate the data in model through tableview?
And are there any better implementations for removeRow() function?

Answer 1

you can use tableWidgetItem->setData(0, Qt::UserRole, "Desired Identity");
it will be always unique even when you sort the rows. refer
QTableWidget find a row through userdata

Answer 2

As the official documentation says ,
There are two ways of approaching sorting in the model/view architecture:
If your model is sortable, i.e, if it reimplements the QAbstractItemModel::sort() function, both QTableView and QTreeView provide an API that allows you to sort your model data programmatically.
The alternative approach, if your model does not have the required interface or if you want to use a list view to present your data, is to use a proxy model to transform the structure of your model before presenting the data in the view
So what happens when you change the sorting depends on how you arrange sorting for your model: either sorting in the view changes the arrangement of rows in the model or it only changes that arrangement for the proxy model.
If you use the proxy model, you can insert there some mapping between proxy model's rows (as the view sees them with the current sorting) and the original model's rows. Or you can just add some mapping between the row and the actual data item for that row in the original model - you can in fact even embed a void* to the data item directly into QModelIndex in your model's reimplementation of QAbstractItemModel::createIndex and then retrieve the pointer to the item from the index passed to methods such as removeRow. Another possibility is to operate with some unique integer identifier of the item instead of the direct pointer to it. It's therefore up to you how which way of mapping between rows and the actual model items to choose.