Arbitrary types conversions for a generic list type variable

[mohit-mittal-cosm]

namespace ns {
    struct C {
            std::string currency;
    };

    struct A {
        std::list<C> object;
    };

    void from_json(const json& j, A& p) {
        j.at("object").at("currency").get_to(p.object.currency); // not sure what should be the syntax here
    }
}

int main()
{
using namespace nlohmann::literals;
json j3 = R"(
{
   
    "object": [
    {
      "currency": "USD",
    },
    {
      "currency": "INR",
    }]
}
)"_json;

auto p2 = j3.template get<ns::A>();
}

I am unsure how to handle the conversion inside from_Json

[mohit-mittal-cosm]

std::vector<C> object;

void from_json(const json& j, A& p) {
    int i = 0;
    for (auto value : j.at("object"))
    {
        value.at("currency").get_to(p.object[i++].currency);
    }
}

converted list to std::vector object;
and tried something like this but no success.

[gregmarr]

The DEFINE_TYPE macros make this very simple:

namespace ns {
    struct C {
        std::string currency;
    };

    NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(C, currency);

    struct A {
        std::list<C> object;
    };

    NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(A, object);
}

int main()
{
using namespace nlohmann::literals;
json j3 = R"(
{
    "object": [
    {
      "currency": "USD"
    },
    {
      "currency": "INR"
    }]
}
)"_json;

auto p2 = j3.get<ns::A>();
}

[mohit-mittal-cosm]

Thank you so much, this worked like a charm. 🙏

[gregmarr]

You're welcome.

[ThePython10110]

For some reason, this doesn't work for me...

EDIT: Never mind, just defined the functions in the wrong namespace.

[gregmarr]

Have you read this section? https://github.com/nlohmann/json?tab=readme-ov-file#conversion-from-stl-containers

[mohit-mittal-cosm]

yes, but it shows how to convert to json, not the other way around. Also i have to convert to a generic list, not a primitive type list.

[mohit-mittal-cosm]

i want to know the implementation of 'from_json' function, for my json being converted to a class instance