How could I find parse_error and is_valid functions?

[barzan-hayati]

I want to check validity of read JSON and check parse error, so I need to use parse_error and is_valid functions. How could I call them? Should I include specific headers? Or in which classes?

Thanks in advance.

[falbrechtskirchinger]

You can find the documentation at https://json.nlohmann.me/.

is_valid() is called accept().

[barzan-hayati]

But this simple example and this one do not run.

    try
    {
        // parsing input with a syntax error
        json::parse("[1,2,3,]");
    }
    catch (json::parse_error& e)
    {
        // output exception information
        std::cout << "message: " << e.what() << '\n'
                  << "exception id: " << e.id << '\n'
                  << "byte position of error: " << e.byte << std::endl;
    }

Error:

error: ‘parse_error’ in ‘using json = using json = class nlohmann::basic_json<> {aka class nlohmann::basic_json<>}’ does not name a type
     catch (json::parse_error& e)
                  ^~~~~~~~~~~

Also for this one:

    json j;
    j["address"]["street"] = "Fake Street";
    j["address"]["housenumber"] = "12";

    try
    {
        int housenumber = j["address"]["housenumber"];
    }
    catch (json::exception& e)
    {
        std::cout << e.what() << '\n';
    }

Error:

error: ‘exception’ in ‘using json = using json = class nlohmann::basic_json<> {aka class nlohmann::basic_json<>}’ does not name a type
     catch (json::exception& e)
                  ^~~~~~~~~

[falbrechtskirchinger]

Please show the complete code.

using json = using json = is not valid syntax.

Also, you're not using the latest version.

[barzan-hayati]

i have install via sudo apt-get install nlohmann-json-dev
The first one:

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

using namespace std;

using json = nlohmann::json;



int main()
{
    try
    {
        // parsing input with a syntax error
        json::parse("[1,2,3,]");
    }
    catch (json::parse_error& e)
    {
        // output exception information
        std::cout << "message: " << e.what() << '\n'
                  << "exception id: " << e.id << '\n'
                  << "byte position of error: " << e.byte << std::endl;
    }
    return 0;
}

and second one:

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

using namespace std;

using json = nlohmann::json;



int main()
{
    json j;
    j["address"]["street"] = "Fake Street";
    j["address"]["housenumber"] = "12";

    try
    {
        int housenumber = j["address"]["housenumber"];
    }
    catch (json::exception& e)
    {
        std::cout << e.what() << '\n';
    }
}

[falbrechtskirchinger]

i have install via sudo apt-get install nlohmann-json-dev

That installs version 2.x.x of the library. The latest release is 3.11.2.

Please install nlohmann-json3-dev if available or download the latest release.