Wt

Hello all!

I am currently attempting to create dbo with composite natural primary key, following tutorial.

I had a common pattern, when Child objects belong to a common Root object, with children having a unique name. So I created a template class BelongingName which functions as an id for each Child. It consists of WString name and Wt::Dbo::ptr foreign key.

With gcc 5.4.0 I get errors with this solution though, which can be divided in 2 categories:

• First, conversion error
  include/Wt/Dbo/Field_impl.h:53:28: error: no matching function for call to ‘Wt::Dbo::sql_value_traits::bind(BelongingName&, Wt::Dbo::SqlStatement*&, int&, const int&)’
  sql_value_traits::bind(value_, statement, column, size_);
  ^

  with note about no known conversion of BelongingName into const char*. I don't mind implementing conversion operator, but I think that's what operator<< specialization is for:
  namespace std{
  ostream& operator<< (ostream& o, const BelongingName& bn)
  {
  return o << bn.getName() << '@' << bn.getRoot()->getName();
  }
  } // namespace std

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• Second, sql_value_traits error:
  include/Wt/Dbo/Field_impl.h:41:35: error: ‘type’ is not a member of ‘Wt::Dbo::sql_value_traits’
  return sql_value_traits::type(session.connection(false), size_);
  ^

  It would seem, that sql_value_traits specialization is required. I was sure though, that BelongingName isn't an actual value, but merely an aggregation, as suggested by:
  namespace Wt{
  namespace Dbo{

  template<class Action>
  void field(Action& action, BelongingName& prop, const Wt::WString& name, int size = -1)
  {
          belongsTo(action, prop.getRoot(), name, NotNull | OnUpdateCascade | OnDeleteCascade);
          field(action, prop.getName(),  name + "_name");
  }
  
  } // namespace Dbo
  } // namespace Wt
  

I'm not sure if this is a bug report, a feature request, both, or just me being stupid :P Could someone clarify?

I'm including an example for reproduction.