QTableView::selectionChanged connect with C++11 lambdas

Infinity

In order to catch the QTableView:::selectionChnaged signal I would like to use connect with C++11 lambdas. I tried the following:

connect(ui->tableView, QOverload<QItemSelection &, QItemSelection &>::of(ui->tableView->selectionChanged()),
            [=](QItemSelection &selected, QItemSelection &deselected) { on_selectionChanged(selected, deselected); });

but I get the following error from the compiler:

.../widgetaddress.cpp:32: Fehler: invalid use of non-static member function ‘virtual void QTableView::selectionChanged(const QItemSelection&, const QItemSelection&)’
32 | connect(ui->tableView, QOverload<QItemSelection &, QItemSelection &>::of(ui->tableView->selectionChanged),

If I use the old connect style like this:

connect(
     ui->tableView->selectionModel(),
     SIGNAL(selectionChanged(const QItemSelection &, const QItemSelection &)),
     SLOT(on_selectionChanged(const QItemSelection &, const QItemSelection &))
    );

it is working.

What am I doing wrong here?

Chris Kawa

You're trying to connect to the view, while the signal is emitted by the selection model (as in your macro version). You're also missing consts and the QOverload is not needed:

connect(ui->tableView->selectionModel(), &QItemSelectionModel::selectionChanged,
        [=](const QItemSelection &selected, const QItemSelection &deselected) { on_selectionChanged(selected, deselected); });

Btw. I would strongly advise to add a third parameter to the connect to scope the life of the connection. Also this lambda seems unnecessary, as you can do just

connect(ui->tableView->selectionModel(), &QItemSelectionModel::selectionChanged, this, &YourClassName::on_selectionChanged);

Christian Ehrlicher

No need to use QOverload at all here since there is no other selectionChanged() function except selectionChanged(const QItemSelection &selected, const QItemSelection &deselected). But you're trying to use selectionChanged(QItemSelection &selected, QItemSelection &deselected) which does not exist.

Infinity

Thanks.

What is the cleanest way to get the value of the selected item? I did it like this:

int selectedRow = ui->tableView->selectionModel()->currentIndex().row();
qDebug() << "Selected Row:" << selectedRow;

QModelIndex addressIdIndex = m_addressModel->index(selectedRow, 0, QModelIndex());
QVariant addressId = m_addressModel->data(addressIdIndex, Qt::DisplayRole);

qDebug() << "addressId:" << addressId.toString();

Is there a cleaner way to get the addressId?

Chris Kawa

Current item and selected item are not the same, so don't use current item for selection.
In a single selection model you can get selected value like this:

if (ui->tableView->selectionModel()->hasSelection()) {
    QVariant addressId = ui->tableView->selectionModel()->selectedRows().first().data();
}

Infinity

Great Thanks.

How can I set the model to single selection? At the same time I would also to set the tableView that only one row can be selected and not single cells. How can I achieve this?

Christian Ehrlicher

@infinity said in QTableView::selectionChanged connect with C++11 lambdas:

How can I set the model to single selection?

By taking a look into the documentation: https://doc.qt.io/qt-5/qabstractitemview.html#selectionBehavior-prop