std::regex and nlohmann::json value

[jm130794]

Hello,

I want to use std::regex with a nlohmann::json value but I have somme problems.

My C++ file :

// g++ -std=c++14 moderncpp_json.cpp -o moderncpp_json
#include <iostream>
#include <regex>
#include "json.hpp"
 
int main(int argc, char *argv[])
{
    using json = nlohmann::json;

    json j = R"({"name": "jmchoulet"})"_json;

    std::regex  r{R"(^(.+)$)"};
    std::smatch m;

    //-- works but need to create a std::string variable !!!                         
    //const std::string value = j["name"].get<std::string>();
    //if (std::regex_match(value, m, r))

    if (std::regex_match(j["name"].get<std::string>(), m, r))
    {   
        std::string s;

        if (m.size())
        {
            std::string tmp = m[1];
            s += "m[1]: " + tmp;
            std::cout << s << std::endl;
        }
    }

    return 0;
}

Compiler g++ output :

$ g++ -std=c++14 moderncpp_json.cpp -o moderncpp_json
moderncpp_json.cpp: In function ‘int main(int, char**)’:
moderncpp_json.cpp:19:60: error: use of deleted function ‘bool std::regex_match(const std::__cxx11::basic_string<_Ch_type, _Ch_traits, _Ch_alloc>&&, std::__cxx11::match_results<typename std::__cxx11::basic_string<_Ch_type, _Ch_traits, _Ch_alloc>::const_iterator, _Alloc>&, const std::__cxx11::basic_regex<_Ch_type, _Rx_traits>&, std::regex_constants::match_flag_type) [with _Ch_traits = std::char_traits<char>; _Ch_alloc = std::allocator<char>; _Alloc = std::allocator<std::__cxx11::sub_match<__gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> > > >; _Ch_type = char; _Rx_traits = std::__cxx11::regex_traits<char>; typename std::__cxx11::basic_string<_Ch_type, _Ch_traits, _Ch_alloc>::const_iterator = __gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> >]’
     if (std::regex_match(j["name"].get<std::string>(), m, r))
                                                            ^
In file included from /usr/include/c++/5/regex:61:0,
                 from moderncpp_json.cpp:3:
/usr/include/c++/5/bits/regex.h:2073:5: note: declared here
     regex_match(const basic_string<_Ch_type, _Ch_traits, _Ch_alloc>&&,

How to avoid this error?

Thank,

Jean-Marc

[nlohmann]

This seems to be this issue: https://stackoverflow.com/questions/33154890/simple-stdregex-search-code-wont-compile-with-apple-clang-std-c14 and related to a change in C++14

As a solution, query a reference with

if (std::regex_match(j["name"].get_ref<std::string&>(), m, r))

[nlohmann]

Does this work for you, @jm130794?

[jm130794]

I just tried. It works ! Thanks 2017-09-04 14:28 GMT+02:00 Niels Lohmann <[email protected]>:

…

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