json stringify

[eladpotok]

The library works very good for my needs. But there is an addition that could be very helpful.
I need a way to stringify the result from the json.dump() function.

For every " or ' that appears in the json, need to be escaped -- " or '.

Thanks,

[nlohmann]

Could you please provide an example? Like a JSON value, the result of dump and what you would expect?

[eladpotok]

Yes.
In case I have this json:

{ "key": "text" , "data": "hello world!" }

I want it to became:

"{ \"key\": \"text\" , \"data\": \"hello world!\" }

and the same for '' to became '\'.
in other words; the json should became to string so if I print it, I will see the special characters .

[nlohmann]

I see. But the resulting string would not be valid JSON text, so adding the backslashes would not make sense for this library.

What you could try (though it would not touch ') would be. This:

#include "json.hpp"
#include <iostream>

using json = nlohmann::json;

int main() {
    json j = R"( { "key": "text" , "data": "hello world!" } )"_json;
    std::cout << json(j.dump()).dump() << std::endl;
}

result:

"{\"data\":\"hello world!\",\"key\":\"text\"}"

[nlohmann]

I think adding the backslashes is out of scope of the library, so I add the "won't fix" label.

[gregmarr]

Sounds like you want this:

json j = ....;
std::string s = j.dump();
json j2(s);  // Create a new JSON object containing the dumped string.
std::string quoted = j2.dump(); // Dump the new JSON object, which quotes the string.

[gregmarr]

Now that I read the previous comments better, this looks to be the same basic idea that @nlohmann posted, including not quoting single quotes.

[eladpotok]

what about the function escape_string that you provided here: https://github.com/nlohmann/json/blob/ec7a1d834773f9fee90d8ae908a0c9933c5646fc/src/json.hpp#L4604-L4697 ? ‫בתאריך יום ד׳, 20 במרץ 2019 ב-17:13 מאת ‪gregmarr‬‏ <‪ notifications@github.com‬‏>:‬

…

Now that I read the previous comments better, this looks to be the same basic idea that @nlohmann <https://github.com/nlohmann> posted, including not quoting single quotes. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1532 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/Aey8wFJCdy1widFAn0nGBYsa1n52wyn7ks5vYlAjgaJpZM4b_bnk> .

-- אלעד פוטוק

[nlohmann]

This function is used internally to escape certain characters as required by

It is called by the dump function.

[nlohmann]

@eladpotok Do you need further assistance on this issue?

[jaredgrubb]

I actually think providing escape_string as a new free-function that people could use for their own purposes (like this one) could be a handy feature.

[gregmarr]

Is that free function any more than this? (I know this is completely unconstrained, and doesn't guarantee strings, but just for the basic idea).

template<typename T> auto escape_string(T &&str) {
    return nlohmann::json{std::forward<T>(str)}.dump();
}

[jaredgrubb]

Yes, it's that, but avoids the mandatory copy (in the const& case). Also, you could argue whether or not the surrounding quote marks should be included or not ("hello" or hello). It's literally just making the "dump_string" function a non-private free function.