{"account":{"name":"John","age":30},"hobbies":["reading","swimming"]}如何通过RapidJSON读取上述json字符串，并且将其中的account字段变成一个新的json字符串

你可以使用RapidJSON库来读取JSON字符串并将其解析为C++对象。以下是一个示例代码，它将读取给定的JSON字符串并将account字段转换为新的JSON字符串：

#include "rapidjson/document.h"
#include "rapidjson/writer.h"
#include "rapidjson/stringbuffer.h"
#include <iostream>
#include <string>

using namespace rapidjson;
using namespace std;

int main() {
    // 定义JSON字符串
    string jsonStr = "{\"account\":{\"name\":\"John\",\"age\":30},\"hobbies\":[\"reading\",\"swimming\"]}";

    // 解析JSON字符串
    Document doc;
    doc.Parse(jsonStr.c_str());

    // 获取account字段
    Value& account = doc["account"];

    // 将account字段转换为新的JSON字符串
    StringBuffer buffer;
    Writer<StringBuffer> writer(buffer);
    account.Accept(writer);
    string accountStr = buffer.GetString();

    // 输出新的JSON字符串
    cout << accountStr << endl;

    return 0;
}

输出结果为：

{"name":"John","age":30}