I have a string that I would like to parse into a json, but _json doesn't seem to work every time.
#include <nlohmann/json.hpp>
#include <iostream>
using nlohmann::json;
int main()
{
// Works as expected
json first = "[\"nlohmann\", \"json\"]"_json;
// Doesn't work
std::string s = "[\"nlohmann\", \"json\"]"_json;
json second = s;
}
The first part works, the second throws terminate called after throwing an instance of 'nlohmann::detail::type_error'
what(): [json.exception.type_error.302] type must be string, but is array.
Adding _json to a string literal instructs the compiler to interpret it as a JSON literal instead.
Obviously, a JSON object can equal a JSON value, but a string cannot.
In these cases, you have to remove _json from the literal, but that makes second a string value hiding inside a JSON object.
So, you call json::parse, like this:
std::string s = "[\"nlohmann\", \"json\"]";
json second = json::parse(s);