How to serialize / deserialize glm::vec3 with union

[4Source]

I wanted to know there is a solution for the from_json to_json with different labels for the glm::vec3 one working with "r", "g", "b" and one with "x", "y", "z"?

Here an example

Vector used as position "x", "y", "z"

#pragma once
#include <glm/glm.hpp>
#include <nlohmann/json.hpp>

namespace glm {
inline void to_json(nlohmann::json &j, const vec3 &vec) { j = nlohmann::json{{"x", vec.x}, {"y", vec.y}, {"z", vec.z}}; }

inline void from_json(const nlohmann::json &j, vec3 &vec) {
    j.at("x").get_to(vec.x);
    j.at("y").get_to(vec.y);
    j.at("z").get_to(vec.z);
}
} // namespace glm

Vector used as color "r", "g", "b"

#pragma once
#include <glm/glm.hpp>
#include <nlohmann/json.hpp>

namespace glm {
inline void to_json(nlohmann::json &j, const vec3 &vec) { j = nlohmann::json{{"r", vec.r}, {"g", vec.g}, {"b", vec.b}}; }

inline void from_json(const nlohmann::json &j, vec3 &vec) {
    j.at("r").get_to(vec.r);
    j.at("g").get_to(vec.g);
    j.at("b").get_to(vec.b);
}
} // namespace glm

I know these are the same values there just a union but I want the different labels in the json file. I think as long not both are needed in same file this maybe work but it definitely not works if both are needed. Has anyone solved this problem?

[gregmarr]

You would need to write your from_json to check for "x" or "r" existing in j and then do the appropriate reads. It's much harder to do to_json, as there would need to be some external switch to tell it which to write.

Alternatively, you could have types like vec3coord and vec3color that just simply derive from vec3.

[4Source]

For the from_json I thought also about this solution but as you sad the to_json is the hard one. I tried it with

using Color = glm::vec3; 

and implement one for Color and one for glm::vec3 but I had linking errors. Would this be different when I just create a derived class Color?

[gregmarr]

Yes, using is just an alias, there is no difference in the types for overload resolution. You need to actually create the derived types. Creating one for Color, using that any place you want the r,g,b values, and leaving vec3 as the default should be sufficient.

[4Source]

Ok thanks I will try this and let you know it works.

[4Source]

I tested it an it works. I added Color and kept the position vector the same.

Vector used as position "x", "y", "z"

#pragma once
#include <glm/glm.hpp>
#include <nlohmann/json.hpp>

namespace glm {
inline void to_json(nlohmann::json &j, const vec3 &vec) { j = nlohmann::json{{"x", vec.x}, {"y", vec.y}, {"z", vec.z}}; }

inline void from_json(const nlohmann::json &j, vec3 &vec) {
    j.at("x").get_to(vec.x);
    j.at("y").get_to(vec.y);
    j.at("z").get_to(vec.z);
}
} // namespace glm

Vector used as color "r", "g", "b"

#pragma once
#include <glm/glm.hpp>
#include <nlohmann/json.hpp>

class Color : public glm::vec3 {
  public:
    using glm::vec3::vec3;

    template <typename V> Color(const V &v) : glm::vec3(v) {}
};

inline void to_json(nlohmann::json &j, const Color &color) { j = nlohmann::json{{"r", color.r}, {"g", color.g}, {"b", color.b}}; }

inline void from_json(const nlohmann::json &j, Color &color) {
    j.at("r").get_to(color.r);
    j.at("g").get_to(color.g);
    j.at("b").get_to(color.b);
}