Re: [boost] boost::python: to-python conversion on polymorphic class

Subject: Re: [boost] boost::python: to-python conversion on polymorphic class
From: Dave Abrahams (dave_at_[hidden])
Date: 2010-12-10 13:40:56

At Fri, 10 Dec 2010 17:12:12 +1100,
Allan Johns wrote:
> 
> Hi,
> 
> Is it possible to register to-python converters for polymorphic types held
> in shared_ptr? This does not seem to work for me.
> 
> I have a virtual base class Object, and derived classes TypedAttribute<T>
> (with method 'value()' that returns a simple type - float, int etc).
> 
> My boost.python registration code looks like so:
> 
> 
>     template<typename Attrib>
>     struct typed_attrib_topython
>     {
>         static PyObject* convert(const Attrib& a)
>         {
>             return bp::incref(bp::object(a.value()).ptr());
>         }
>     };
> 
> 
>     template<typename T>
>     struct TypedAttribBind
>     {
>         typedef TypedAttribute<T> attrib_t;
> 
>         TypedAttribBind()
>         {
>             boost::python::to_python_converter<attrib_t,
> typed_attrib_topython<attrib_t> >();
>         }
>     };
> 
> 
> However this doesn't work. 

Doesn't work how?

You shouldn't need to do anything special for shared_ptrs; just return
them.  Don't register converters.  See shared_ptr.cpp in
Boost.Python's libs/python/test/ directory.

-- 
Dave Abrahams
BoostPro Computing
http://www.boostpro.com