[Swig-user] Wrapping a Class SWIG Can't See

[Rob S. <rob...@si...>]

We use a macro to define some classes.  SWIG doesn't appear to
expand the macro -- it can't parse the header, at any rate -- so
SWIG doesn't know anything about the generated class.  I created
a class template which uses CRTP to expose the generated class to
SWIG.  I used %template to name the specialization of that
template back to the original name.  (See below.)

All of that seems to go well.  Unfortunately, SWIG doesn't
understand that functions that return the macro-generated type
should be turned into instances of the class template
specialization.  That would suggest typemaps are in order, but I
don't know how to tell SWIG to create a proxy object for the
template-based type.

Here's a simplified form of the interface file:

%{
#include "Example.h"
#include "wrapper.h"
%}

%include "wrapper.h"
%template(Example) wrapper<Example>;

%pythoncode
%{
   Example_FOO = Example_fromString('FOO')
   Example_BAR = Example_fromString('BAR')
%}

Here's a simplified version of wrapper.h:

template <class T>
struct wrapper : T
{
   wrapper(T const & that_i);

   wrapper(typename T::value const value_i);

   ~wrapper();

   typename T::value
   getValue() const;

   std::string
   toString() const;

   wrapper
   operator |(wrapper const & rhs_i) const;

   static wrapper
   fromString(std::string const & name_i);
};

What I need is a typemap(out) for real Example instances (not the
renamed ones from the %template directive), so that when a
function returns an Example, SWIG will create a proxy of a
wrapper<Example> instead.  I would hate to have to
%ignore/%extend all functions that return an Example.

I don't think I will need a typemap(in) to handle the case in
which a function expects an Example because a wrapper<Example> can
be assigned to an Example.

-- 
Rob Stewart                           rob...@si...
Software Engineer                     http://www.sig.com
Susquehanna International Group, LLP  using std::disclaimer;