在json中将空ptree提升为map

Question

我正在使用boost ptree创建一个json字符串，这是我的代码：

int main()
{
    ptree pt;
    ptree commands;


    pt.put<int>("mCommandID", 1);
    pt.put<int>("mTimeSent", 0);
    pt.add_child("commands", commands);
    write_json(cout,pt);
}

但是此代码的输出是：

{
    "mCommandID": "1",
    "mTimeSent": "0",
    "commands": ""
}

我喜欢它：

{
    "mCommandID": "1",
    "mTimeSent": "0",
    "commands": "{}"
}

怎么可能？

Answer 1

你想在JSON中使用JSON，所以你想要write_json两次：

<强> Live On Coliru

#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/json_parser.hpp>
#include <iostream>

using namespace boost::property_tree;

std::string to_json_string(ptree const& pt)
{
    std::ostringstream oss;
    json_parser::write_json(oss, pt, false);
    return oss.str();
}

int main()
{
    ptree pt;
    ptree commands;

    pt.put<int>("mCommandID", 1);
    pt.put<int>("mTimeSent", 0);
    pt.put("commands", to_json_string(ptree {}));
    pt.put("more-commands", to_json_string(pt)); // a crude example

    json_parser::write_json(std::cout, pt);
}

打印

{
    "mCommandID": "1",
    "mTimeSent": "0",
    "commands": "{}\n",
    "more-commands": "{\"mCommandID\":\"1\",\"mTimeSent\":\"0\",\"commands\":\"{}\\n\"}\n"
}