Sort in column added to qtreeview

[SwePtr]

I have inherited QFileSystemModel like this.
It seems to work, kinda. But I have problem sorting.

//fileinfobaseclass.h
class FileBaseClass : public QFileSystemModel{
public:    
FileBaseClass();
FileBaseClass(QObject * parent);
~FileBaseClass();
int columnCount(const QModelIndex& parent = QModelIndex()) const;
QVariant data(const QModelIndex& index,int role) const;
};

.

//fileinfobaseclass.cpp
QVariant FileBaseClass::data(const QModelIndex& index,int role) const{
 if(!index.isValid()){
    return QFileSystemModel::data(index,role);}
if(index.column()==columnCount()-1){
    QFileInfo *qf=new QFileInfo(QFileSystemModel::fileInfo(index).absoluteFilePath());
QString fileInfo;
    switch(role)  {
    case(Qt::DisplayRole): {
        if ( qf->isWritable ()){
            fileInfo+="rw";
        }
        if ( qf->isSymLink ()){
            fileInfo+="s";
        }
        return fileInfo;
    }
    default:{}
  }
 }
return QFileSystemModel::data(index,role);
}

.
//In MainWindow
treeViewModel->sort ( 4 , Qt::AscendingOrder );