Библиотека JSON, чтение файла

#include <iostream>
 
#include <nlohmann/json.hpp>
 
using json = nlohmann::json;
 
int main()
{
    json config = {
        "Settings": {
            "AutoReload"      :true,
            "CheckingUpdates" :false
        }
    };
    
    const auto& settings = config["Settings"];
    
    const bool auto_reload 
        = settings.at("AutoReload").get<bool>();
    
    const bool checking_updates 
        = settings.at("CheckingUpdates").get<bool>();
 
    std::cout << "auto_reload = "      << auto_reload << '\n';
    std::cout << "checking_updates = " << checking_updates << '\n';
    
}

#include <iostream>
#include <jsoncpp/json/json.h> // or something
 
using namespace std;
 
int main() {
    // create the characters array
    Json::Value ch;
    ch[0]["name"] = "Jabberwock";
    ch[0]["chapter"] = 1;
    ch[1]["name"] = "Cheshire Cat";
    ch[1]["chapter"] = 6;
    ch[2]["name"] = "Mad Hatter";
    ch[2]["chapter"] = 7;
 
    // create the main object
    Json::Value val;
    val["book"] = "Alice in Wonderland";
    val["year"] = 1865;
    val["characters"] = ch;
 
    cout << val << '\n';
}

// rapidjson/example/simpledom/simpledom.cpp`
#include "rapidjson/document.h"
#include "rapidjson/writer.h"
#include "rapidjson/stringbuffer.h"
#include <iostream>
 
using namespace rapidjson;
 
int main() {
    // 1. Parse a JSON string into DOM.
    const char* json = "{\"project\":\"rapidjson\",\"stars\":10}";
    Document d;
    d.Parse(json);
 
    // 2. Modify it by DOM.
    Value& s = d["stars"];
    s.SetInt(s.GetInt() + 1);
 
    // 3. Stringify the DOM
    StringBuffer buffer;
    Writer<StringBuffer> writer(buffer);
    d.Accept(writer);
 
    // Output {"project":"rapidjson","stars":11}
    std::cout << buffer.GetString() << std::endl;
    return 0;
}

        std::ifstream src(filename);
        if(!src)
            throw std::runtime_error(
                "[load] can not open the file '" + filename + "'"
            );
 
        Json     jsn;
        src   >> jsn;
 
        // дальше работаем с jsn

    const auto& settings = gotten_obj ["Settings"];
    
    const bool auto_reload 
        = settings.at("AutoReload").get<bool>();
    
    const bool checking_updates 
        = settings.at("CheckingUpdates").get<bool>();
 
    std::cout << "auto_reload = "      << auto_reload << '\n';
    std::cout << "checking_updates = " << checking_updates << '\n';

#include <iostream>
#include <fstream>
#include <stdexcept>
#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/json_parser.hpp>
namespace bpt = boost::property_tree;
 
 
int main()
{
    try
    {
        std::ifstream ifs{"in.json"};
        if (!ifs.is_open())
        {
            throw std::runtime_error{"Unable to open file"};
        }
 
        bpt::ptree pt;
        bpt::read_json(ifs, pt);
        bool sar = pt.get<bool>("Settings.AutoReload");
        bool scu = pt.get<bool>("Settings.CheckingUpdates");
        std::cout << std::boolalpha << sar << '\n' << scu << std::endl;
 
    }
    catch (std::exception const& exc)
    {
        std::cerr << "Exception: " << exc.what() << std::endl;
    }
}

// taken from ranges-v3
template<typename T>
struct static_const
{
    static constexpr T value{};
};