我将如何在此类（初学者代码）中使用聚合？

Question

我想了解聚合，所以我尝试编写一个简单的测试代码，但它在我的编译器中不起作用，有时它可以在线运行。

主代码：

#include <iostream>
#include <string>    
#include "player.h"
#include "game.h"
using namespace std;

int main(){ 
    game game;
    game.playGame();

    return 0;
}

game.cpp 代码：

#include "game.h"
#include "player.h"

game::game(){
    player.setBalance(0); 
}

void game::playGame(){
  cout << "playing game." ;  //just for debugging
}

game.h 的代码：

#ifndef GAME  
#define GAME
#include <iostream>
using namespace std;

class game{

  private:
    player player;

  public:
    game();
    void playGame();

}; 


#endif

player.cpp 的代码：

#include "player.h"

 player::player(){
   balance = 0;
 }

 player::player(int theBalance){
   balance = theBalance;
 }

 int player::getBalance(){
   return balance;
 }

 void player::setBalance(int theBalance){
   balance = theBalance;
 }

player.h 的代码：

 #ifndef PLAYER // used on headers 
 #define PLAYER

 class player{

     private:
     int balance;

   public:

     player();
     player(int);
     int getBalance();
     void setBalance(int);
 }; 

 #endif

我认为问题可能出在标题上。 我得到的错误是：

In file included from main.cpp:5:0:
game.h:10:12: error: declaration of 'player game::player' [-fpermissive]
 player player;

In file included from main.cpp:4:0:
player.h:5:7: error: changes meaning of 'player' from 'class player' [-fpermissive]
class player{
       ^~~~~~

Answer 1

我认为问题出在类游戏中，因为它不知道类玩家，使用前向声明或只是在game.h中写#include "player.h"