对派生类的"vtable"的未定义引用

我是一个完全的初学者，我已经在论坛上阅读了有关此主题的各种帖子，但我仍然不确定我哪里出错了。

这是我的基类：

class room {
    protected:
        int doors;
        string name;
        room *north;
        room *east;
        room *south;
        room *west;
    public:
        room(int numDoors, string rmName);
        virtual string getName();
        virtual void setRoom(int numDoors, string rmName);
        void setConnect(room *room1, room *room2, room *room3, room *room4);
};
room::room(int numDoors, string rmName) : doors(numDoors), name(rmName) {}
string room::getName() {
    return this->name;
}
void room::setConnect(room *room1, room *room2, room *room3, room *room4) {
    this->north = room1;
    this->east = room2;
    this->south = room3;
    this->west = room4;
    return;
}

这是我的派生类：

class treasureRoom : public room {
    protected:
        string chest[5];
    public:
        treasureRoom() : base(4, "The Mad King's Hoard") {}
        void setChest(string &loot1, string &loot2, string &loot3, string &loot4, string &loot5);
        string getChest(int i);
};

void treasureRoom::setChest(string &loot1, string &loot2, string &loot3, string &loot4, string &loot5) {
    this->chest[0] = loot1;
    this->chest[1] = loot2;
    this->chest[2] = loot3;
    this->chest[3] = loot4;
    this->chest[4] = loot5;
    return;
}
string treasureRoom::getChest(int i) {
    return this->chest[i];
}

我已经多次尝试实施论坛上讨论的有关此类错误的解决方案，但我仍然缺少一些关键的重要性。任何帮助将不胜感激！