为什么提振属性树write_json节省一切，字符串？是否有可能改变这种状况？ [英] Why boost property tree write_json saves everything as string? Is it possible to change that?

问题描述

我想使用boost属性树write_json序列化，这样可以节省一切为字符串，这并不是说数据是错误的，但我需要每次都显式转换他们，我想别的地方使用它们。 （像Python或其他C ++ JSON（非增压）库）

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 and I want to use them somewhere else. (like in python or other C++ json (non boost) library)

下面是一些示例code和我所得到的根据地区不同：

here is some sample code and what I get depending on locale:

boost::property_tree::ptree root, arr, elem1, elem2;
elem1.put<int>("key0", 0);
elem1.put<bool>("key1", true);
elem2.put<float>("key2", 2.2f);
elem2.put<double>("key3", 3.3);
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_somewhare_else = ss.str();

和 my_string_to_send_somewhere_else 为某事。像这样的：

{
    "path1" :
    {
       "path2" :
       [
            {
                 "key0" : "0",
                 "key1" : "true"
            },
            {
                 "key2" : "2.2",
                 "key3" : "3.3"
            }
       ]
    }
}

反正是有其保存为值，比如：
KEY1：真正的或KEY2：2.2

推荐答案

好吧，我解决了这个样子，（当然也不会适合每个人，因为它是一个黑客位，即需要进一步工作）。

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).

我写我自己write_json功能（简单地复制文件，json_parser.hpp和json_parser_write.hpp到我的项目），并在json_parser_write.hpp修改以下行：

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. 注释行37 - 逃避报价'


2. 改变行76 - 这样它不添加引号了：
   流＆LT;＆LT; CH（''）所述;＆lt;数据＆所述;＆下; C​​H（''）; ==>流＆LT;＆LT;数据;

比起值将除字符串正确保存，所以我写了自定义的翻译吧：

---

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

template <typename T>
struct my_id_translator
{
    typedef T internal_type;
    typedef T external_type;

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

和使用简单的保存字符串：

and simply saved string using:

elem2.put<std::string>("key2", "asdf", my_id_translator<std::string>());

完整的程序：

#include <iostream>
#include <string>
#include <sstream>

#include <boost/property_tree/ptree.hpp>

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

template <typename T>

struct my_id_translator
{
    typedef T internal_type;
    typedef T external_type;

    boost::optional<T> get_value(const T &v) { return  v.substr(1, v.size() - 2) ; }
    boost::optional<T> 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<std::string, std::string> elem1;
        elem1.put<int>("int", 10 );
        elem1.put<bool>("bool", true);
        elem2.put<double>("double", 2.2);
        elem2.put<std::string>("string", "some string", my_id_translator<std::string>());

        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;
}

结果：）

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

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