Qt: Sorting is wrong when using QSortFilterProxyModel on number strings and getting wrong column text

Question

i have simple model view treeview with QSortFilterProxyModel proxy to sort the columns and QStandardItemModel as the model
in each columns there are string that gets sor

Answer 1

That's because by default, QSortFilterProxyModel sorts by DisplayRole. If that returns a string, it will sort the string. To have the model sort by some other value, define a custom sort role in the source model and set it on the proxy:

class MyModel {
   ...
   enum Role {
      SortRole=Qt::UserRole
   };
   QVariant data( ... ) const {
       ...
       switch ( role ) {
       case Qt::DisplayRole:
           return value as string;
       case SortRole:
           return value as int;
       }
   }
};

...
sortfilterproxy->setSortRole( MyModel::SortRole );

Your second question: What is m_model? The source model, or the sortfilterproxymodel? The former is never changed by sorting, the sorting happens only in the proxy.