结构体包含由子结构体转换成的json字符串，无法反解回结构体

[stupied-ies]

以“六年级-三班-某学生”为例，学生由结构体转换为json字符，作为班级的成员； 班级由结构体转换为json字符，作为年级的成员； 由年级json字符无法解析出classParm成员变量，解析出的结构只有"{"

#include "mainwindow.h"
#include <QApplication>
#include <iostream>
#include "../iguana/iguana/json.hpp"
// 六年级-三班-某学生
struct Person
{
    std::string  name;
    int          age;
};
REFLECTION(Person, name, age);

struct Class   
{
    int classID;
    std::string personParm;
};
REFLECTION(Class, classID, personParm)

struct Grade   
{
    int gradeID;
    std::string classParm;  
};
REFLECTION(Grade, gradeID, classParm)

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
//    MainWindow w;
//    w.show();
    Person p;
    p.age = 10;
    p.name = "suli";
    iguana::string_stream pp;
    iguana::json::to_json(pp, p);
    std::cout << pp.str() << std::endl;
    Person res_p;
    iguana::json::from_json(res_p, pp.str().c_str());

    Class c;
    c.classID = 3;
    c.personParm = pp.str();
    iguana::string_stream cc;
    iguana::json::to_json(cc, c);
    std::cout << cc.str() << std::endl;
    //const char* dd= "{\"classID\":3,\"personParm\":\"{\\\"name\\\":\\\"suli\\\",\\\"age\\\":10}\"}";
    Class res_c;
    iguana::json::from_json(res_c, cc.str().c_str());

    Grade g;
    g.gradeID = 6;
    g.classParm = cc.str();
    iguana::string_stream gg;
    iguana::json::to_json(gg, g);
    std::cout << gg.str().c_str() << std::endl;
    Grade res_g;
    iguana::json::from_json(res_g, gg.str().c_str());

    Grade res;
    iguana::json::from_json(res, gg.str().c_str());
    return a.exec();
}