QAbstractProxyModel tutorial? or advice?

Hi,

I got all excited when I saw this: http://labs.trolltech.com/blogs/2008...-of-modelview/ then found the source link is broken :-(

I have a QSqlTableModel which is being displayed in a QTreeView. It works nicely.

I want to allow the user to 'groupBy' a particular column, generally a text field.

So as a first stab I wrote a QAbstractProxyModel to just pass things straight thru. I got it largely working except the SQLTableModel implements canFetchMore which I had to muck about with in rowCount and then all my troubles began.

I could share code and get help that way, but before that -- is there a good tutorial anywhere that will help me? I am particularly interested in understanding how createIndex is supposed to work and why it doesn't accept a parent parameter, even tho QModelIndex needs one....

Anyway thanks for any pointers you can give me with this.

Cheers,
Mark

Perhaps it would be better to share my code.

The following works ok for me. In my main application I create a QSQLTableModel, do a select() on it and then while it canFetchMore I fetchMore (shouldn't the view do this?).

Then I create my GroupByModel and setSourceModel to the QSQLTableModel before then adding a QSortFilterProxyModel and setting its source model to my GroupByModel and then, finally, setModel on my QTableView to the QSortFilterProxyModel.

Is this code "correct" as a pass-through proxy (i.e. it doesn't do anything at all at the moment, just reflects the source model).

I'm about to start modifying it to create a mapping from the sqlmodel and would like to be sure I'm not doing things incorrectly....

Any advice gratefully received....

Code:

---

// Proxy model ... transparent at the moment
class GroupByModel : public QAbstractProxyModel
{
    Q_OBJECT
 
private:
    bool *groupBy;
 
public:
 
    GroupByModel(bool *groupBy, QObject *parent = NULL) : QAbstractProxyModel(parent), groupBy(groupBy) {
        setParent(parent);
    }
    ~GroupByModel() {}
 
    // create a model index, don't bother with parent for now
    // since -1,-1 has no parent and all others have a parent of -1.-1
    QModelIndex index(int row, int column, const QModelIndex & = QModelIndex()) const {
        return createIndex(row,column);
    }
 
    // parent is at -1, -1. All others have a parent of -1, -1
    QModelIndex parent(const QModelIndex &index) const {
        // we are at the top, return an invalid parent
        if (index.column() == -1 && index.row() == -1) return QModelIndex();
        else return createIndex(-1,-1);
    }
 
    QModelIndex mapToSource(const QModelIndex &proxyIndex) const {
 
        // we use the same co-ords for now, so map to the same
        return sourceModel()->index(proxyIndex.row(),proxyIndex.column());
    }
 
    // source model should be the same as ours
    QModelIndex mapFromSource(const QModelIndex &sourceIndex) const {
        return index(sourceIndex.row(), sourceIndex.column());
    }
 
    // same columns as source please
    int columnCount(const QModelIndex &parent = QModelIndex()) const {
        return sourceModel()->columnCount(sourceModel()->index(parent.row(), parent.column()));
    }
 
    int rowCount(const QModelIndex &parent = QModelIndex()) const {
        if (parent.row() == -1 && parent.column() == -1) {
            return sourceModel()->rowCount(sourceModel()->index(parent.row(), parent.column()));
        } else
            return 0;
    }
 
    // does this index have children?
    bool hasChildren(const QModelIndex &index) const {
        // if it is the root index (-1,-1) - it might have children
        if (index.row() == -1 && index.column() == -1 && rowCount(createIndex(-1,-1)))
            return true;
        else
            return false;
    }
 
};

---

http://www.slideshare.net/mariusbu/q...views-in-depth

Is failry good.

http://gitorious.org/qtgroupingproxy/qtgroupingproxy

For future reference, in case someone stumbles across this thread, the kde guys have created a grouping proxy, it is at the url above.