C++/Eclipse undefined reference 问题

Question

我遇到了 Eclipse/C++ 中明显的链接器错误(“ undefined reference ”)的问题。下面显示的所有类都可以正常编译，除了一个 PlayGame.cpp，它给出了“ undefined reference ”错误(也在下面显示)。

下面是相关的类和代码片段。

PlayerFactory.h

播放器工厂.cpp

游戏.h

游戏.cpp

// constructor for game:

Game::Game (const PlayerFactory& factory)

{

       cout << " constructor" << endl;

}

游戏.cpp

// start of code for game where error occurs

#include "Game.h"

#include "PlayerFactory.h"

int main() {
   try

   {

      PlayerFactory factory;

      Game game (factory);  <== undefined reference error
      ...

上面一行给出了错误“对 `Game(PlayerFactory const&)' 的 undefined reference ”

导致此错误的原因是什么，如何更正？

Answer 1

class 声明的默认可见性是私有(private)的。所以 Player 和 PlayerFactory 类的所有成员函数都是 private —— 客户端无法访问。您需要将它们公开。

Player.h

#ifndef PLAYER_H 
#define PLAYER_H
class Player  
{  
public:
   virtual ~Player() {  
       cout << "Player destructor called" << endl;  

   }  
   virtual void Player::PlayerMakeMove(){  
       cout << "make move" << endl;  
   }  


};  
#endif // PLAYER_H

PlayerFactory.h

#ifndef PLAYERFACTORY_H
#define PLAYERFACTORY_H
class PlayerFactory  
{  
public:
   virtual ~PlayerFactory() {  
       cout << "PlayerFactory destructor called" << endl;  
   }  

   virtual std::auto_ptr<Player> PlayerFactory::MakePlayerX() const{  

       return PlayerFactory::MakePlayer('x');  
   }  

   virtual std::auto_ptr<Player> PlayerFactory::MakePlayerO() const{  
       return PlayerFactory::MakePlayer('o');  

   }  

   std::auto_ptr<Player> PlayerFactory::MakePlayer (char letter) const{  
       auto_ptr<Player> pt( new Player() );  
       return pt;  
   }  
};
#endif // PLAYERFACTORY_H

此外，Game::Play() 缺少 return 语句。

Outcome Game::Play() {  
  cout << " play" << endl;  
  return PlayerXWon;
}

请根据需要添加所需的 header 、前向声明和using 语句(我在这里跳过它们)。