On Fri, Jun 28, 2019 at 2:16 PM Nicholas Devenish <ndeven...@gmail.com> wrote:
>
> I want to get the same python instance back for subsequent calls to
> the C++ function e.g. I want this to work for the C++ structure below:
>
> import ident_ext
> o = ident_ext.Owner()
> assert o.get() is o.get()
>
> How can I get this behaviour in boost::python? It looked like call
> policies was the right sort of place to look, but can't get that to
> behave how I want. I can get this to work in pybind11 but not boost
> (and unfortunately our project is heavily dependent on boost::python).
> My working c++ is:
>
> #include <boost/python.hpp>
> #include <iostream>
> using namespace boost::python;
>
> class Something {
> public:
> void name(void) { std::cout << this << std::endl; }
> };
>
> class Owner {
> Something *_shared = nullptr;
>
> public:
> Something &get() {
> if (_shared == nullptr) {
> _shared = new Something();
> }
> return *_shared;
> }
> };
>
> BOOST_PYTHON_MODULE(ident_ext) {
> class_<Something>("Something").def("name", &Something::name);
> class_<Owner>("Owner").def("get", &Owner::get, return_internal_reference<>());
> }
Maybe store a wrapping bp::object in addition to the Something ptr,
then always return the same bp::object? That’s how I did it. Ok, you
would probably have to create a wrapper for Something just for this. I
don’t know how feasible this is.
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