Converting C++ class to JSON

Question

I\'d like to create a JSON string containing the instance variables of my class.

For example,

class Example {  
    std::string string;  
    std::ma         


        

Answer 1

nlohmann::json allows you to have arbitrary type conversions. It's described here https://nlohmann.github.io/json/features/arbitrary_types/ in more detail.

class Example {  
    std::string string;  
    std::map map;  
    std::vector vector;

    // Add this to your code.
    NLOHMANN_DEFINE_TYPE_INTRUSIVE(Example, string, map, vector);
};

Since the class members are private you can use the macro: NLOHMANN_DEFINE_TYPE_INTRUSIVE(...). I don't know whether it works with std::map or std::vector but it works with primitive types.

Like here:

struct MyStruct {
    std::string name;
    int number;

    NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(MyStruct, name, number);
};

Note how I used NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE because the struct members are public.

Now I can call the to_json(Json& j, const MyStruct& s) function like:

MyStruct s;
s.name = "test";
s.number = 11;

nlohmann::json j;
s.to_json(j, s);
std::cout << j << std::endl;
// {"name":"test","number":11}