Reimplement data() in QSqlQueryModel

[john_erlandsson]

Hi!

I am experimenting with a subclass of QSqlQueryModel. Since I wanted to change the background color in the ListView, I reimplemented the data method

QVariant BrowseWoTableModel::data( const QModelIndex &item, int role ) const
{
    if( role == Qt::BackgroundColorRole )
    {
        return Qt::green;
    }
 
    else if( role == Qt::DisplayRole )
    {
        return record( item.row() ).value( item.column() );
    }
 
    return QVariant();
}

QVariant BrowseWoTableModel::data( const QModelIndex &item, int role ) const
{
    if( role == Qt::BackgroundColorRole )
    {
        return Qt::green;
    }

    else if( role == Qt::DisplayRole )
    {
        return record( item.row() ).value( item.column() );
    }

    return QVariant();
}

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This works for setting the background color, but fails in displaying the data.

What am I missing here?

//John

[ChrisW67]

Your override returns null QVariants for roles like Qt::FontRole, Qt::TextColorRole and Qt::ForegroundRole.

Try something like this:

QVariant BrowseWoTableModel::data( const QModelIndex &item, int role ) const
{
    if (!item.isValid())
        return QVariant();
 
    if( role == Qt::BackgroundColorRole )
        return Qt::green;
    else
        return QSqlQueryModel::data(item, role);
}

QVariant BrowseWoTableModel::data( const QModelIndex &item, int role ) const
{
    if (!item.isValid())
        return QVariant();

    if( role == Qt::BackgroundColorRole )
        return Qt::green;
    else
        return QSqlQueryModel::data(item, role);
}

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[john_erlandsson]

The "similar threads" box held the anwser.

QVariant BrowseWoTableModel::data( const QModelIndex &item, int role ) const
{
    QVariant ret = QSqlQueryModel::data( item, role );
 
    if( role == Qt::BackgroundColorRole )
    {
        return Qt::green;
    }
 
    return ret;
}

QVariant BrowseWoTableModel::data( const QModelIndex &item, int role ) const
{
    QVariant ret = QSqlQueryModel::data( item, role );

    if( role == Qt::BackgroundColorRole )
    {
        return Qt::green;
    }

    return ret;
}

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This works. But i dont understand why. Where does the data come from?

[ChrisW67]

Line 3 gathers the result you would received from a base QSqlQueryModel and that is returned unless the role is BackgroundColorRole.