Hi Michele,

Thanks for the pointers, but unfortunately I don't think they apply in 
my case. It seems that boost support for iterators was written *only* 
with STL-like iterators in mind. You have to have begin() and end() and 
to be able to dereference the iterator. I can't do it (or I don't know 
how to do it).
In contrast, my iterators are more like python iteration sequence, with 
only one method: get_next(), which returns the next object in the 
container *and* advances the iterator at the same time. I can't  
dereference this iterator, as you would do in STL.

In fact, this seems to be so close to the python iteration model, that a 
simple approach should be doable:

BOOST_PYTHON_MODULE(vegetables)
{
    class_<Garden> ("Garden")
        .def("get_potatoes", &Garden::get_potatoes)
        .def("get_tomatoes", &Garden::get_tomatoes)
    ;
    class_<TomatoIter> ("TomatoIter")
        .def("__iter__", &TomatoIter::get_next)
    ;
}

That at least compiles - unlike all my previous attempts that generate 
three pages of template errors - but python complain:

TypeError: iter() returned non-iterator of type 'Tomato'

so now I am trying to figure out how to tell boost that get_tomatoes 
returns an iterator ...

Thomas


Michele De Stefano wrote:
>  Thomas,
> 
>  I think the answer is here:
>  http://www.boost.org/doc/libs/1_40_0/libs/python/doc/tutorial/doc/html/python/iterators.ht
ml
> 
>  but you should modify your "Garden" class in order to support "begin"
>  and "end" iterators for "tomatoes" and "potatoes".
> 
>  With these modifications:
> 
>  class Garden {
>  public:
>    typedef ....      Tomato_Iter;
>    typedef ....      Potato_Iter;
> 
>    Tomato_Iter   tomatoes_begin();
>    Tomato_Iter   tomatoes_end();
>    Potato_Iter   potatoes_begin();
>    Potato_Iter   potatoes_end();
>  };
> 
>  you can expose your Garden class as here:
> 
>  class_<Garden>("Garden")
>      .property("tomatoes", range(&Garden::tomatoes_begin, &Garden::tomatoes_end))
>      .property("potatoes", range(&Garden::potatoes_begin,
>  &Garden::potatoes_end));
> 
>  At this point, in Python, you should be able to write:
> 
>  for potato in garden.potatoes:
>     .... and do here whatever you want ...
> 
>  It's the best I can suggest
> 
> 
>  2009/11/6 Thomas Daniel <thomasd57@[...].com>:
>    
> > I am having trouble wrapping a container that can hold multiple object types
> > and therefore has multiple iterator types.
> >
> > My C++ library has these classes:
> >
> > class Tomato;
> > class Potato;
> > class Garden {
> >   Iter<Tomato>   get_tomatoes();
> >   Iter<Potato>   get_potatoes();
> > };
> >
> > template<class T>
> > class Iter {
> >   T get_next();
> > };
> >
> > which allows to write:
> >
> > Iter<Potato> potatoes = garden.get_potatoes();
> > while (Potato potato = potatoes.get_next()) {
> >  cout << potato.name();
> > }
> >
> > I am trying to use boost to wrap it so that I can write in python:
> >
> > for potato in garden.get_potatoes():
> >  print potato.name()
> >
> > Any pointers how to achieve this with boost?
> >
> >
> >
> >
> >
> > _______________________________________________
> > Cplusplus-sig mailing list
> > Cplusplus-sig@[...].org
> > http://mail.python.org/mailman/listinfo/cplusplus-sig
> >
> >     
> 
> 
> 
>    
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