QAbstractProxyModel tutorial? or advice?

[liversedge]

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

[liversedge]

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....

// 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;
    }
 
};

// 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;
    }

};

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[liversedge]

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

Is failry good.

[liversedge]

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.