Qt signal emit in addressbook - qt

Question

I am learning the Model-View in Qt by the AddressBook example. https://doc.qt.io/qt-5/qtwidgets-itemviews-addressbook-example.html
And I find something interesting. The code construct a TableModel class besed on QAbstractTableModel. In the override setData function, it emit the dataChanged signal. But, there is no signal emit in removeRows/insertRows. Then, how can these function update the View.
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;
}
bool TableModel::setData(const QModelIndex &index, const QVariant &value, int role)
{
if (index.isValid() && role == Qt::EditRole) {
int row = index.row();
QPair<QString, QString> p = listOfPairs.value(row);
if (index.column() == 0)
p.first = value.toString();
else if (index.column() == 1)
p.second = value.toString();
else
return false;
listOfPairs.replace(row, p);
emit(dataChanged(index, index));
return true;
}
return false;
}

Answer 1

Make note of function calls beginRemoveRows() and endRemoveRows() in the function removeRows() of your posted code.
The beginRemoveRows() function, emits a signal rowsAboutToBeRemoved(). This is how connected views can know about the deletion and the underlying connected views must handle before data is removed.
Look the note in below documentation:
https://doc.qt.io/qt-5/qabstractitemmodel.html#beginRemoveRows