[C++-sig] Pointer to existing Python object

[Andreas Beyer]

Hi,

I just want to bring this issue back on the table. I still didn't get a 
brilliant idea how to solve it.

So far, I see only this option:
- Wrap B, in particular wrap B.get().
- In get() create the actual python object, like:
    python::object py_a(B::get());
- Store those objects in a map.
- When B_wrap.get() gets called again, check if a python object already 
exists and return it.

However, in my real-world application I had to wrap quite a lot of 
methods returning As. I also have methods returning vectors of A_ptr, 
which makes it even more enoying. (I would have to wrap the 
vector<A_ptr>, too.)

What is this has_back_reference doing? Is that somehow related to my 
problem? (I regret that I don't really understand what it is doing, as I 
don't know what a "predicate metafunction" is.)
Just adopting the example at 
http://www.boost.org/libs/python/doc/v2/has_back_reference.html is not 
really a solution, because my instances of A are created inside the C++ 
code (by factory methods in class B). I would have to be very intrusive 
and make the actual class B aware of Python/boost::python for adopting 
the above solution.

I know that boost::python is collecting the shared pointers somewhere. 
Is it possible to use that mechanism somewhow for solving my problem? 
Any ideas?

Thanks!!
    Andreas