Why does Boost property tree write_json save everything as string? Is it possible to change that?

Question

I\'m trying to serialize using boost property tree write_json, it saves everything as strings, it\'s not that data are wrong, but I need to cast them explicitly every time a

Answer 1

Ok, I've solved it like this, (of course it won't suite for everybody, as it is a bit of a hack, that need further work).

---

I've wrote my own write_json function (simply copied the files, json_parser.hpp and json_parser_write.hpp to my project) and modified the following lines in json_parser_write.hpp:

1. commented line 37 - escaping the quote '"'
2. changed line 76 - so that it doesn't add quotes anymore: stream << Ch('"') << data << Ch('"'); ==> stream << data;

---

Then values will be saved properly except for strings, so I wrote custom translator for it:

template 
struct my_id_translator
{
    typedef T internal_type;
    typedef T external_type;

    boost::optional get_value(const T &v) { return  v.substr(1, v.size() - 2) ; }
    boost::optional put_value(const T &v) { return '"' + v +'"'; }
};

and simply saved string using:

elem2.put("key2", "asdf", my_id_translator());

complete program:

#include 
#include 
#include 

#include 

#include "property_tree/json_parser.hpp" // copied the headers

template 

struct my_id_translator
{
    typedef T internal_type;
    typedef T external_type;

    boost::optional get_value(const T &v) { return  v.substr(1, v.size() - 2) ; }
    boost::optional put_value(const T &v) { return '"' + v +'"'; }
};

int main(int, char *[])
{
    using namespace std;
    using boost::property_tree::ptree;
    using boost::property_tree::basic_ptree;
    try
    {
        ptree root, arr,elem2;
        basic_ptree elem1;
        elem1.put("int", 10 );
        elem1.put("bool", true);
        elem2.put("double", 2.2);
        elem2.put("string", "some string", my_id_translator());

        arr.push_back( std::make_pair("", elem1) );
        arr.push_back( std::make_pair("", elem2) );
        root.put_child("path1.path2", arr);

        std::stringstream ss;
        write_json(ss, root);
        std::string my_string_to_send_somewhere_else = ss.str();

        cout << my_string_to_send_somewhere_else << endl;

    }
    catch (std::exception & e)
    {
        cout << e.what();
    }
    return 0;
}

result :)

{
    "path1":
    {
        "path2":
        [
            {
                "int": 10,
                "bool": true
            },
            {
                "double": 2.2,
                "string": "some string"
            }
        ]
    }
}