几个未定义的引用

Question

我正在用C ++编写宠物模拟器，最初是用Visual C ++编写的。过渡期很艰难，但除了以下事实外，它主要起作用了：

undefined reference to `Pet::Pet(double, double, int, int, int, std::string, ...);'
undefined reference to `Pet::eat(int)'
7 more

所以这是我的标题（Pet.h）：

#ifndef __Pet__
#define __Pet__ //picked this up learning Visual C++
                //not sure if good or not

#include <string>

class Pet{
public:
    bool dead;
    int health;

    //etc

    void eat(int amount);
    void play(int time);
    void pet(int times);
    void bathe();
    void buy(std::string item, int quantity);
    void stats();

    void hurt();

    Pet(double happiness_, double hunger_, int weight_, int age_,
        int cleanliness_, string name_, string type_, int food_, int money_, bool dead);
};

#endif

这是我的班级（Pet.cpp）：

#include "Pet.h"
#include <string>
#include <iostream>

//not sure if this practice is discouraged or not
using namespace std;

Pet::Pet(double happiness_, double hunger_, int weight_, int age_, int cleanliness_,
        string name_, string type_, int food_, int money_, bool dead_){
    hapiness = happiness_;
    hunger = hunger_;
    age = age_;
    cleanliness = cleanliness_;
    name = name_;
    type = type_;
    dead = dead_;
    health = 100;

    inventory.food = food_;
    inventory.money = money_;
}

void Pet::eat(int amount){
    if(hunger <= 45){
        cout << "You feed " << name << ".\n";

        hunger += amount;
        inventory.food -= amount;

        return;
    }
    cout << "Your pet is already full!";
}
//etc

对于巨大的文字墙感到抱歉，但有很多可能是错误的。