QAbstractItemModel

[Jeff Barnes]

Hello all,
I'm trying to remember how to use a QAbstractItemModel with a QListView.

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    ui->lvGroups->setModel(&m_groupModel);
}
...
void MainWindow::on_actionNew_Group_triggered()
{
    GroupData grp(-1, "New Group");
    m_groupModel.addGroup(grp);
}
...
void GroupModel::addGroup(const GroupData &data)
{
    qDebug() << "GroupModel::addGroup";
    beginInsertRows(QModelIndex(), m_groups.size(), m_groups.size());
    qDebug() << "appending group data";
    m_groups.append(data);
    qDebug() << "appended";
    endInsertRows();
}
...
QVariant GroupModel::data(const QModelIndex &index, int role) const
{
    qDebug() << "GroupModel::data" << index.row();
    Q_UNUSED(role);
    if (!index.isValid())
        return QVariant();
    return m_groups.at(index.row()).name();
}

I don't see the group name in the list view, nor the appropriate qDebug() message in data(). I do see qDebug messages from addGroup().

I must be missing something stupid. Could somebody help me out, please?

[SGaist]

Hi,

That's because you are returning the same string for every role. You should be more selective. Return that string only for the DisplayRole and EditRole.

[Jeff Barnes]

@SGaist
Thanks.
But data() never gets called.

[SGaist]

Wrong model sizes ?

Based on the code you shared, it's only guesses.

Are you sure you correctly implemented all the required method ?

You can check your model with the Qt model tester.

[Jeff Barnes]

Bingo. Wrong model sizes. The QItemModel wizard puts logic that isn't appropriate for a QListView. If one isn't careful they will not implement rowCount() and columnCount() correctly. Pretty subtle mistake, actually.
First of all, it will generate a compiler warning. Second, while the !parent.isValid() should be used to return the model size, return 0 makes me think it should always return 0. For QListViews, it should return the model size.
The wizard could be more helpful, IMO.

Mo' coffee.

int RestaurantModel::rowCount(const QModelIndex &parent) const
{
    if (!parent.isValid())
        return 0;

    // FIXME: Implement me!
}

int RestaurantModel::columnCount(const QModelIndex &parent) const
{
    if (!parent.isValid())
        return 0;

    // FIXME: Implement me!
}