rv_policy::reference_internal dose not work for make_iterator

[lf-shaw]

I want to modify the underlying data using iterator, but it does not work.

#include <vector>

#include <nanobind/trampoline.h>
#include <nanobind/stl/bind_vector.h>
#include <nanobind/make_iterator.h>

struct Foo {
    size_t x;

    Foo(int x) : x(x) {}
};

struct Demo {
    Demo() {
        for (size_t i = 0; i < 10; i++) {
            data.push_back({i});
        }
    }

    int sum() const {
        int s = 0;
        for (auto v : data) {
            s += v.x;
        }
        return s;
    }

    std::vector<Foo> data;
};

namespace nb = nanobind;

using FooVector = std::vector<Foo>;
NB_MODULE(t1, m) {
    nb::bind_vector<FooVector, nb::rv_policy::reference_internal>(m, "FooVector");

    nb::class_<Foo>(m, "Foo").def(nb::init<int>()).def_rw("x", &Foo::x);

    nb::class_<Demo>(m, "Demo")
        .def(nb::init<>())
        .def("sum", &Demo::sum)
        .def(
            "__iter__",
            [](Demo& s) {
                return nb::make_iterator(nb::type<Demo>(), "iterator", s.data.begin(),
                                         s.data.end());
            },
            nb::keep_alive<0, 1>(), nb::rv_policy::reference_internal);
}

in Python

import t1

d = t1.Demo()

d.sum()  # 45

for r in d:
    r.x *= 2

d.sum()  # 45, expected 90

Did I make a mistake?

Thank you all!

[lf-shaw]

yes, I made a mistake. I place nb::rv_policy::reference_internal in the wrong place.

    nb::class_<Demo>(m, "Demo")
        .def(nb::init<>())
        .def("sum", &Demo::sum)
        .def(
            "__iter__",
            [](Demo& s) {
                return nb::make_iterator<nb::rv_policy::reference_internal>(
                    nb::type<Demo>(), "iterator", s.data.begin(), s.data.end());
            },
            nb::keep_alive<0, 1>());