[Qt-interest] Returning data from models

[phil prentice]

Hi
  If this is more a C++ question then a QT one, then I apologise up front now 
and you can ignore me!!!  I have a declared a class derived from 
QAbstractListModel.  The code works fine, but as a novice I am just trying to 
improve what I have.  My problem is that I have a list data associated with 
my model and I am using the roles UserRole+n to access the data.
Here is some of the code:-

class BottomArrowModel : public QAbstractListModel
{
    Q_OBJECT

public:
    BottomArrowModel(QObject *parent = 0);

    /* Over-ride functions. */
    bool setData(const QModelIndex &index, const QVariant &value,
                                              int role = Qt::EditRole);
    bool insertRows(int position, int rows,
                              const QModelIndex &index = QModelIndex());
    bool removeRows(int position, int rows,
                              const QModelIndex &index = QModelIndex());
    int rowCount(const QModelIndex &parent = QModelIndex()) const;
    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const;
    inline void setZoomFactor(int zoom) {m_zoomFactor = zoom;
                                                emit layoutChanged(); };
    inline int zoomFactor() {return m_zoomFactor;};

private:
    int m_zoomFactor; /* 1, 2 or 4 */
    QStringList instNameList;  /* My data consists of a list of items each */
    QStringList facNameList;  /* one having an entry for the 6 items on */
    QStringList remarkList;    /* the left. */
    QStringList commentList;
    QStringList componentList;
    QStringList signalList;
};


bool BottomArrowModel::setData(const QModelIndex &index,
                                        const QVariant &value, int role)
{
  if (index.isValid())
  {
    switch(role)
    {
      case Qt::UserRole: /* Instrument name. */
        instNameList.replace(index.row(), value.toString());
        break;
      case Qt::UserRole+1: /* Facility name. */
        facNameList.replace(index.row(), value.toString());
        emit dataChanged(index, index);
          /* Let the views know of changes..data changed signal emitted. */
        break;
      case Qt::UserRole+2: /* Remark. */
        remarkList.replace(index.row(), value.toString());
        emit dataChanged(index, index);
          /* Let the views know of changes..data changed signal emitted. */
        break;
      case Qt::UserRole+3: /* Comment. */
        commentList.replace(index.row(), value.toString());
        emit dataChanged(index, index);
          /* Let the views know of changes..data changed signal emitted. */
        break;
      case Qt::UserRole+4: /* Component. */
        componentList.replace(index.row(), value.toString());
        emit dataChanged(index, index);
          /* Let the views know of changes..data changed signal emitted. */
        break;
      case Qt::UserRole+5: /* Signal. */
        signalList.replace(index.row(), value.toString());
        emit dataChanged(index, index);
          /* Let the views know of changes..data changed signal emitted. */
        break;
      default: /* Ignore anything else. */
        return false;
    }
    return true;
  }
  return false;
}


/* Use model to obtain data. */
QVariant BottomArrowModel::data(const QModelIndex &index, int role) const
{
  if (!index.isValid())
    return QVariant();

  if (index.row() >= facNameList.size())
    return QVariant();

  switch(role)
  {
    case Qt::UserRole: /* Instrument name. */
      return instNameList.at(index.row());
      break;
    case Qt::UserRole+1: /* Facility name. */
      return facNameList.at(index.row());
      break;
    case Qt::UserRole+2: /* Remark string. */
      return remarkList.at(index.row());
      break;
    case Qt::UserRole+3: /* Comment string. */
      return commentList.at(index.row());
      break;
    case Qt::UserRole+4: /* Component string. */
      return componentList.at(index.row());
      break;
    case Qt::UserRole+5: /* Signal string. */
      return signalList.at(index.row());
      break;
    default: /* Ignore anything else. */
      return QVariant();
  }
}

My concern lies in that the above works OK, but what if I had say 100 
different items to update and they were all of a different type.  I am sure 
that there is probably a better way, maybe using QLIst<T>?

The thing is ..is that data and setData uses the object QVariant to pass the 
data in and out.  Is there a way to pass a class object (myClass) as Qvariant 
and store these objects in a list QList<T>.  Then my delegate and view etc 
could access the model the once to get the data for one item in the list in 
the form of myClass.  That class could be used to access the individual items 
of data in the model.  I could also probably set the data in a similar 
read/write way.

What I have got just does not seem very clever...can anybody educate me here, 
or point me to an example?

Thanks

Phil Prentice