paulftw/hiberlite

enums as object fields

psydevascender opened this issue · 5 comments

psydevascender commented

how to make enum class (or just old school enums) serializable?

enum class Gender {
    male, female
};

class Person {

Gender gender_;

friend class hiberlite::access;

    template <class Archive>
    void hibernate(Archive & ar) {
        ar & HIBERLITE_NVP(gender_);
  }

gives compilation error
Visitor.h:12:4: Member reference base type 'ARGender' is not a structure or union
static void hibernate(A& a, C& c) { c.hibernate(a); }
I assume that it lacks template specialization similar to POD types like int, etc

d-led commented

one can think of an extensible conversion. Inspired by hiberlite some time ago I've made something similar for json:

namespace picojson {
    namespace convert {

        template<> struct value_converter<Example::Status> {
            static value to_value(Example::Status v) {
                return value(static_cast<double>(v));
            }
            static void from_value(value const& ov, Example::Status& v) {
                if ( ov.is<double>() )
                    v = Example::Status(static_cast<int>(ov.get<double>()));
            }
        };


    }
}

haven't looked at hiberlite for a long time, but it should be doable. Will look at it in spare time

d-led commented

include/some_types.h might give a hint on how one would extend the user code to support custom type conversion

psydevascender commented

Privet Dmitriy
Yes, I really do like your picojson's way to make value_converter template specialization.
But I really don't understand now how to apply this to the hiberlite?
It uses its own macros to make name-value pairs without converter class and without to_value()/ from_value() methods.
So where should I plug the code?
To make it extendible and not to modify the library's headers directly? Ideally just to plug in some additional template specializations in my own .h file

d-led commented

Privet Sergey :)

As with picojson, before registering your class with hiberlite, your template specialization of template<class A> void ::hiberlite::hibernate as it's done in the HIBERLITE_DEF_DB_ATOM macro should be visible. I think, if this works, it'll just go into the README. There probably should be no need to extend hiberlite source

  • 👍1
psydevascender commented

cool, thanks for the example :) I tried something similar but completely forgot about the namespace scope. And now it works perfectly!
p.s IMHO definitely worth adding it to the README

  • 👍1