里面有5个文件
//folder.h
#ifndef FOLDER_H
#define FOLDER_H
#include <string>
#include <iostream>
#include "message.h"
#include <set>
using namespace std;
class Message;
class Folder{
public:
Folder() = default;
void addMsg(Message * rhs);
void remMsg(Message * rhs);
void print_msg()const;
private:
set<Message*> messages;
};
#endif
//message.h
#ifndef MESSAGE_H
#define MESSAGE_H
#include <string>
#include <vector>
#include <new>
#include <set>
#include "folder.h"
using namespace std;
class Folder;
class Message{
friend class Folder;
public:
explicit Message(const string &str = "");
Message(const Message&);
Message& operator=(const Message &);
~Messa