Converting C++ class to JSON

JSON Spirit would allow you to do it like so:

Object addr_obj;addr_obj.push_back( Pair( "house_number", 42 ) );addr_obj.push_back( Pair( "road",         "East Street" ) );addr_obj.push_back( Pair( "town",         "Newtown" ) );ofstream os( "address.txt" );os.write( addr_obj, os, pretty_print );os.close();

Output:

{    "house_number" : 42,    "road" : "East Street",    "town" : "Newtown"}

The json_map_demo.cpp would be a nice place to start, I suppose.

Any good C++ JSON library should do this and it is sad to see that they don't -- with the exception of ThorsSerializer and apparently Nosjob as mentioned in this question.

Of course, C++ does not have reflection like Java, so you have to explicitly annotate your types:
(copied from the ThorsSerializer documentation)

#include "ThorSerialize/JsonThor.h"#include "ThorSerialize/SerUtil.h"#include <map>#include <vector>#include <string>#include <iostream>class Example {    std::string string;    std::map<std::string, std::string> map;    std::vector<int> vector;    // Allow access to the class by the serialization library.    friend class ThorsAnvil::Serialize::Traits<Example>;    public:        Example(std::string const& s, std::map<std::string, std::string> const& m, std::vector<int> const& v)            : string(s), map(m), vector(v)        {}};// Define what members need to be serilizableThorsAnvil_MakeTrait(Example, string, map, vector);

Example Usage:

int main(){    using ThorsAnvil::Serialize::jsonExport;    using ThorsAnvil::Serialize::jsonImport;    Example     e1 {"Some Text", {{"ace", "the best"}, {"king", "second best"}}, {1 ,2 ,3, 4}};    // Simply serialize object to json using a stream.    std::cout << jsonExport(e1) << "\n";    // Deserialize json text from a stream into object.    std::cin  >> jsonImport(e1);}

Running:

{    "string": "Some Text",    "map":    {        "ace": "the best",        "king": "second best"    },    "vector": [ 1, 2, 3, 4]}

You cannot do better than this in C++.

I wrote a library which designed to solve your problem.However, it is a very new project, not stable enough.Feel free to take a look, the homepage is here::

https://github.com/Mizuchi/acml

In your example, you have to add one line like this:

ACML_REGISTER(Example, ,(string)(map)(vector));

in order to tell the library which member you want to dump.Since C++ have no reflection.And you must give a way to access the member, either use public member level or use friend class.

And later you just need to do sth like this:

string result = acml::json::dumps(any_object);

would become::

{    "string": "the-string-value",    "map":    {        "key1": "val1",        "key2": "val2"    },    "vector":    {        "type": "std::vector",        "size": "4",        "0": "1",        "1": "2",        "2": "3",        "3": "4"    }}

As you see, JSON array is not implemented yet.And everything becomes string now.