json::parse string is order

[ApacheWang]

Hello nlohmann, I have a question, when using json::parse string, the output json string is sorted by key, is there a way to let json save the key sequence of the original string

[gregmarr]

Answered in the FAQ https://nlohmann.github.io/json/home/faq/

[nlohmann]

To quote:

By default, the library does not preserve the insertion order of object elements. This is standards-compliant, as the JSON standard defines objects as "an unordered collection of zero or more name/value pairs".

If you do want to preserve the insertion order, you can specialize the object type with containers like tsl::ordered_map (integration) or nlohmann::fifo_map (integration).

[nlohmann]

@ApacheWang Do you need further assistance?

[nlohmann]

When #2258 is merged, it will be possible to use type ordered_json which maintains the insertion order of object keys.

[nlohmann]

Done.

[gbartl]

I am trying to do the same thing here and I am getting loads of compilation errors, here is my snippet:

#include <nlohmann/json.hpp>
#include <iostream>

using json = nlohmann::ordered_json;

int main(void) {
    json j = json::parse("{\"b\":2,\"a\":1}");
    std::cout<< j <<std::endl;
    return 0;
}

Am I using it wrong?
gcc version 8.3.1

[nlohmann]

This is a bug tracked in #2315. There is a branch linked where the bug is fixed. I will merge it to develop soon.