QTableView with a checkbox

[maxpower]

Is it possible for a QTableView showing a model from a MySQL DB to have a column with checkboxes that get turned into text (Y,N) in the DB? In other words, I would like a column that contains checkboxes instead of having the user have to enter Y or N.

mAx

[wysota]

Yes. You need to implement a custom delegate which will handle that.

[KingFish]

You don't need a new delegate for that. In your model, simply react to the Qt::CheckStateRole (in data() and setData() for the appropiate columns).

[maxpower]

What do you mean by "react to ...?" I have tried this:

model->setData(model->index(0, 7), "Y", Qt::CheckStateRole)

to no avail. I want the checkbox in column 7 which is recorded in the DB as Y or N. Is the above sorta right or do I have to subclass QSqlTableModel and reimplement the data and setdata functions?

Thanks
mAx

[wysota]

I'd stick with the delegate thing. Otherwise you'll have to reimplement the model without really needing it. The delegate will give you much more flexibility.

[maxpower]

Okay, so I see in the docs how to subclass ItemDelegate and make my own. However, it appears you assign the delegate for the whole view. I only want to change the delegate for one column. How is this accomplished?

mAx

[jpn]

Qt 4.2 introduces new functions:

• QAbstractItemView::setItemDelegateForRow()
• QAbstractItemView::setItemDelegateForColumn()

In Qt 4.1 you'll just have to check the column of the passed model index:

void MyItemDelegate::delegateFunction(const QModelIndex& index, ...)
{
    if (index.isValid() && index.column() == INTERESTING_COLUMN)
    {
        // appropriate column in question, do the custom thing
    }
    else
    {
        // pass to the base class implementation
        QItemDelegate::delegateFunction(index, ...);
    }
}

void MyItemDelegate::delegateFunction(const QModelIndex& index, ...)
{
    if (index.isValid() && index.column() == INTERESTING_COLUMN)
    {
        // appropriate column in question, do the custom thing
    }
    else
    {
        // pass to the base class implementation
        QItemDelegate::delegateFunction(index, ...);
    }
}

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[maxpower]

Okay, thanks for the help I am getting close now. I converted the included exmaple for the sponbox delegate to a checkbox delegate and compiled it and it worked great. However, once I changed the code fome setItemDelegate to setItemDelegateForColumn, it no longer worked at all. Do I need to change something in the example code for the custom delegate to work with just one column? I am using 4.2.

Thanks
mAx

[maxpower]

Anybody have an idea? I just tried 4.2.1 but no love there either.

mAx

[jpn]

Looks like QAbstractItemView::itemDelegateForRow/Column are not used pretty much for anything (yet?)... Anyway, I already gave you a solution which works with old good "normal" delegates.. and it has been discussed earlier..

[maxpower]

Okay, I edited the spinbox example again and with your code it properly displays a checkbox in the first column. However, I tried to use the exact same code in my program and it doesn't work. The column and row headers are present but there is no data, nor checkboxes or even grid lines. What did i do wring?

Thanks
mAx

[Georgest]

Is it possible for a QTableView showing a model from a MySQL DB to have a column with checkboxes that get turned into text (Y,N) in the DB? In other words, I would like a column that contains checkboxes instead of having the user have to enter Y or N.

mAx

Without delegates:

class MyModel : public QSqlQueryModel {
    Q_OBJECT
public:
    MyModel(QObject *parent = 0);
    Qt::ItemFlags flags(const QModelIndex &index) const;
    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const;
........
};
 
Qt::ItemFlags MyModel::flags(const QModelIndex &index) const {
    Qt::ItemFlags flags = QSqlQueryModel::flags(index);
    if (index.column() == aColWithCheckbox)
        flags |= Qt::ItemIsUserCheckable;
    else
        flags |= Qt::ItemIsEditable;
    return flags;
} 
 
QVariant MyModel::data(const QModelIndex &index,  int role) const {
  QVariant value = QSqlQueryModel::data(index, role);
  if (role == Qt::CheckStateRole && index.column() == aColWithCheckbox)
    return (QSqlQueryModel::data(index).toInt() != 0) ? Qt::Checked : Qt::Unchecked;
  else
    return value;
}

class MyModel : public QSqlQueryModel {
    Q_OBJECT
public:
    MyModel(QObject *parent = 0);
    Qt::ItemFlags flags(const QModelIndex &index) const;
    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const;
........
};

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

QVariant MyModel::data(const QModelIndex &index,  int role) const {
  QVariant value = QSqlQueryModel::data(index, role);
  if (role == Qt::CheckStateRole && index.column() == aColWithCheckbox)
    return (QSqlQueryModel::data(index).toInt() != 0) ? Qt::Checked : Qt::Unchecked;
  else
    return value;
}

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[wysota]

You're changing the model here which is... well... at least controversial when it comes to the MVC paradigm.

BTW. The model is to be editable so you should subclass QSqlTableModel and also reimplement setData(). Now imagine someone wants to have another view (or access the database through the model) without the checkboxes... Or the column might allow NULLs

Of course I don't say that you can't do it this way, I only say you should do it with a delegate, as you'll be modifying only the user interaction this way. I wrote about it earlier in the thread.

Just for completeness - a third way would be to use a proxy model that would translate between the bool and the checkstate role. That would be my second best suggestion (as it doesn't change the source model).

[Georgest]

The bounds between View and Model are the conventionalities... Qt4 provides for changing font, color, alignment in model, so it can be useful.

For NULLs there is Qt::ItemIsTristate.

setData needs to be reimplemented of course:

bool MyModel::setData(const QModelIndex &index,  const QVariant &value, int /* role */) {
    if (index.column() ......)
        return false;
 
    QModelIndex primaryKeyIndex = QSqlQueryModel::index(index.row(), 0);
    int id = QSqlQueryModel::data(primaryKeyIndex).toInt();
    //clear();
    bool ok;
    QSqlQuery query;
    if (index.column() == 1) {
        query.prepare("update employee set name = ? where id = ?");
        query.addBindValue(value.toString());
        query.addBindValue(id);
    .......
    }else if(index.column() == aColWithCheck) {
        query.prepare("update employee set married = ? where id = ?");
        query.addBindValue(value.toInt());
        query.addBindValue(id);
    }
    ok = query.exec();
    refresh();
    return ok;
}

bool MyModel::setData(const QModelIndex &index,  const QVariant &value, int /* role */) {
    if (index.column() ......)
        return false;

    QModelIndex primaryKeyIndex = QSqlQueryModel::index(index.row(), 0);
    int id = QSqlQueryModel::data(primaryKeyIndex).toInt();
    //clear();
    bool ok;
    QSqlQuery query;
    if (index.column() == 1) {
        query.prepare("update employee set name = ? where id = ?");
        query.addBindValue(value.toString());
        query.addBindValue(id);
    .......
    }else if(index.column() == aColWithCheck) {
        query.prepare("update employee set married = ? where id = ?");
        query.addBindValue(value.toInt());
        query.addBindValue(id);
    }
    ok = query.exec();
    refresh();
    return ok;
}

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ItemIsUserCheckable in flags() and CheckStateRole in data() achieve the interesting feature: checkbox is clicked -> text label is changed in cell.

Proxy model 'Bool to CheckStateRole' is realy the best i think

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