vector-pickle.cpp

/*
 * higher-up library:
 */

class Foo {
  std::shared_ptr<Vector<double>> v;
  
  template<class Archive>
  void serialize(Archive &archive) {
    // defer polymorphic serialisation of Vector
    archive(v);
  }
};

/*
 * binding code:
 */

// concrete functions for a pure virtual class
class PyVector : public Vector<double> {
public:
  // a few methods like this:
  virtual void plus(const Vector<double>& x) override {
    PYBIND11_OVERRIDE_PURE(void, Vector<double>, plus, x);
  }

  template<class Archive>
  void save(Archive &archive) const {
    // cereal API for saving, e.g. serialise the pickle dump (untested!)

    py::gil_scoped_acquire gil;

    py::object pickle = py::module_::import("pickle");
    py::object pickled = pickle.attr("dumps")(py::cast(this));
    std::string result = pickled.cast<std::string>();

    archive(result);
  }

  template<class Archive>
  void load(Archive &archive) {
    py::gil_scoped_acquire gil;

    py::object pickle = py::module_::import("pickle");
    std::string pickled;
    archive(pickled); // load string

    // un-pickle to python object
    py::object loaded = pickle.attr("loads")(pickled);

    // at this point, cereal already constructed our PyVector instance
    // (through its polymorphism), but how do we tell it to "own" the
    // un-pickled Python object?
  }
};

CEREAL_REGISTER_POLYMORPHIC_RELATION(Vector<double>, PyVector);