我Album在“album.h”中有一个这样的课程：
#include "song.h"
class Album
{
public:
Album(string _id, string _title, string _singer, float _price, vector<Song> _songs) : id(_id), title(_title), singer(_singer), price(_price), songs(_songs), availableAlbums(10) {}
void add_song(Song s){ songs.push_back(s); }
void add_availableAlbums(int added){ availableAlbums += added; }
string get_id(){ return id; }
string get_singer(){return singer;}
private:
string id;
string title;
string singer;
float price;
vector <Song> songs;
int availableAlbums;
};
和Song“song.h”中的一个类，如下所示：
#include "album.h"
class Song
{
public:
Song(string _numOfSong, string _title, string _singer, string _duration, float …