Converting C++ class to JSON

Question

I'd like to create a JSON string containing the instance variables of my class.

For example,

class Example {       std::string string;       std::map<std::string, std:string> map;       std::vector<int> vector;   }; 

would become:

{     "string":"the-string-value",     "map": {         "key1":"val1",         "key2":"val2"     },     "vector":[1,2,3,4] } 

I've looked into several C++ libraries for creating JSON and they all seem incredibly complex. I'd like something similar to Javascript's JSON.stringify(object). In other words just pass a std::map to it and receive a string. The map could contain other maps, vectors, lists, strings, numbers and bools.

What's the nicest way to do this?

Thanks for your help.

Edit

I've looked into the following:

json spirit, jsoncpp, zoolib, JOST, CAJUN, libjson, nosjob, JsonBox, jsonme--

Which I understand I can construct a separate JSON object as in an answer below and convert to JSON I'd like to be able to store my stuff in standard collections and convert.

Edit 2

Okay, scrap the idea of serializing a class since it appears that's impossible with C++'s lack of reflection.

Is there a nice way to convert a std::map containing std:maps, std::vectors, std::lists, numbers, strings, and bools to JSON without having to change datatypes or copying data to a new datatype?

Thanks.

Answer 1

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.