Derived classes from json class

[bradacsa]

I just wrote two custom classes based on nlohmann::json:
class Cookie : public nlohmann::json <- this can handle cookies, chops up cookie strings from headers, etc...
class JsonFile : public nlohmann::json <- this is nothing else but the json class joined up with a fstream to make easier to load and save json from file.
My problem is, if I create a Cookie like
Cookie A1("A1=d=AQABBN3h6GUCECMYqmLClG1pK2uiuaCh0xoFEgABCAEq6mUTZutMb2UBAiAAAAcI3OHoZXSoivI&S=AQAAAqvfHaGFJkLfQ07HNDr2tH0;Expires=Thu, 6 Mar 2025 213629 GMT;"); and I try to pass it into a JsonFile like

FileHandlers::JsonFile cJsonFile(cookieJson); cJsonFile["Cookies"]["A1"] = A1;

it says "terminate called after throwing an instance of 'nlohmann::json_abi_v3_11_2::detail::type_error' what(): [json.exception.type_error.302] type must be string, but is object".

The Cookie works fine, chopping and parsing are done and if I do it like this cJsonFile["Cookies"]["A1"] = A1.dump(); and it works as well. ChatGPT suggested to me that I should write an operator Cookie& operator=(const nlohmann::json& other) and pass the things trough here but this will be not triggered with cJsonFile["Cookies"]["A1"] = A1;.

Has anyone encountered this problem?