Qt checkboxes in QTableView

Question

I'm using this code to query sqlite and put the results in a QTableView.

//MainWindow.cpp
void MainWindow::on_pushButton_clicked()
{
    QSqlQueryModel * modal=new QSqlQueryModel();
    connOpen();
    QSqlQuery* qry=new QSqlQuery(mydb);

    qry->prepare("select * from database");
    qry->exec();

    modal->setQuery(*qry);

    //from stack
    modal->insertColumn(0);

    ui->tableView->setModel(modal);

    //from stack
    ui->tableView->resizeColumnsToContents();

    int p;
    for(p=0; p<modal->rowCount(); p++)
    {
        ui->tableView->setIndexWidget(modal->index(p,0),new QCheckBox());
    }

    connClose();
    qDebug() <<(modal->rowCount());
}

I've seen several examples of the web for adding checkboxes to a column, but I'm not quite sure what to use for my simple example.

• This answer suggests a few lines that doesn't seem standard.
• There are more examples like this and this one that appear to outline what I need, but it's unclear to where you place the code.

What I intend to do is to have column 1 checkable. On next btn press, If checked those rows of data get written to a file.

I still need to understand how to loop thru the selected data, or perhaps I need to get the ids of the checked rows and do another query.

Questions:

• How do you add 1 column of editable checkboxes to QTableView?
• How do you loop through values in the QTableView data, so values of the checked rows can be accessed?
• How do you check all/none?

Answer 1

I think the best way to have a column of checkable cells is to create your item model, e.g. by subclassing the QSqlQueryModel. You must reimplement the flags() method to make checkable the cells.

Also you need to reimplement the data() method to return the check state and the setData() method and to set the check state. You must implement your own logic to keep track of the check state of every rows (e.g. using an array of Qt::CheckState that you must initialize and resize when the model data changes).

Yuo can start with something like this:

class MyModel : public QSqlQueryModel
{
public:

    Qt::ItemFlags flags(const QModelIndex & index) const
    {
        if(index.column() == 0)
             return QSqlQueryModel::flags(index) | Qt::ItemIsUserCheckable;
        return QSqlQueryModel::flags(index);
    }

    QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const 
    {
        if(index.column() == 0 && role == Qt::CheckStateRole)
        {
            //implement your logic to return the check state 
            //....
        }
        else
            return QSqlQueryModel::data(index, role);
    }

    bool setData(const QModelIndex & index, const QVariant & value, int role = Qt::EditRole)
    {
        if(index.column() == 0 && role == Qt::CheckStateRole)
        {
            //implement your logic to set the check state 
            //....
        }
        else
            QSqlQueryModel::setData(index, value, role);
    }
};

Se also:

• Model Subclassing
• QAbstractItemModel documentation