c++ - 链接器错误 - undefined reference

Question

我正在创建一个程序，但是当我运行它时出现这些错误:

/tmp/ccYLF4IM.o: In function `main':
maingame.cpp:(.text+0x13): undefined reference to `Human::Human()'
maingame.cpp:(.text+0x1f): undefined reference to `Orc::Orc()'
maingame.cpp:(.text+0x99): undefined reference to `Orc::~Orc()'
maingame.cpp:(.text+0xac): undefined reference to `Orc::~Orc()'
maingame.cpp:(.text+0xc5): undefined reference to `Human::~Human()'
maingame.cpp:(.text+0xdf): undefined reference to `Human::~Human()'
collect2: ld returned 1 exit status

我查看了我的代码，我正在同时运行所有 .cpp 文件和 .h 文件。我不确定是什么问题。我知道还有其他关于此的问题，但我似乎无法找到我正在寻找的答案。我已经检查了所有内容的大小写，甚至删除了所有内容并重新开始以确保。对此的任何帮助将不胜感激。谢谢

//main.cpp
#include "Human.h"
#include "Orc.h"

using namespace std;

//Main.cpp
int main()
{
    //Character cc;
    Human H;
    Orc O;
    char choice;
    char userC;
    cout << "Welcome!\n";
    cout << "" << endl;

    cout << "Pick your choice:\n";
    cout << "A -- Human\n";
    cout << "B -- Orc\n";
    cin >> choice;

    return 0;
}

---

//Character.h
#ifndef CHARACTER_H
#define CHARACTER_H

#include <iostream>
#include <string>

using namespace std;

class Character
{
    protected:
                float characterTotal;
    public:                 
                virtual int createCharacter() = 0; //Pure virtual function
                Character();
                ~Character();   
};

#endif

---

//Character.cpp
#include "Character.h"
Character::Character()
{
//ctor
}

Character::~Character()
{
//dtor
}

---

//human.h
#ifndef HUMAN_H
#define HUMAN_H

#include "Character.h"

using namespace std;

class Human : public Character 
{
    private:
                int characterStrength;
                int characterDexterity;
                int characterIntelligence;
                string characterType;
                int characterTotal;

    public:
                Human();//Constructor 
                                ~Human();

                int getStrength ()
                {
                    cout << "Enter a number from 0 to 18\n";
                    cin >> characterStrength;

                    return characterStrength;
                }

                int getDexterity ()
                {
                    cout << "Enter a number from 0 to 18\n";
                    cin >> characterDexterity;

                    return characterDexterity;
                }

                int getIntelligence ()
                {
                    cout << "Enter a number from 0 to 18\n";
                    cin >> characterIntelligence;

                    return characterIntelligence;
                }

                string getType ()
                {
                    cout << "Please choose one of the following\n";
                    cout << "A -- Paladin \n";
                    cout << "B -- Ranger \n";
                    cout << "C -- Wizard \n";\
                    cin >> characterType;

                    return characterType;
                }

                virtual int createCharacter()
                {
                    characterTotal = characterStrength + characterIntelligence + characterDexterity;
                    return characterTotal;
                }
};

#endif

---

//Human.cpp
#include "Human.h"
Human::Human()
{
//ctor
}

Human::~Human()
{
//dtor
}

---

//orc.h
#ifndef ORC_H
#define ORC_H

#include "Character.h"

using namespace std;

class Orc : public Character
{
    private:
                int characterStrength;
                int characterDexterity;
                int characterIntelligence;
                int chaD;
                int chaI;
                int chaS;
                string characterClan;
                int characterTotal;

    public:
                Orc(); //Constructor
                        ~Orc();

                int getStrength()
                {
                    cout << "Enter a number between 0 to 18\n";
                    cin >> chaS;
                    characterStrength = chaS + 2;

                    return characterStrength;
                }

                int getDexterity()
                {
                    cout << "Enter a number between 0 to 18\n";
                    cin >> chaD;
                    characterDexterity = chaD - 2;

                    return characterDexterity;
                }

                int getIntelligence()
                {
                    cout << "Enter a number between 0 to 18\n";
                    cin >> chaI;
                    characterIntelligence = chaI - 2;

                    return characterIntelligence;
                }

                string getClan()
                {
                    cout << "Please choose one of the following\n";
                    cout << "A -- Barbarian \n";
                    cout << "B -- Berserker \n";
                    cout << "C -- Vanguard \n";\
                    cin >> characterClan;

                    return characterClan;
                }

                virtual int createCharacter()
                    {
                        characterTotal = characterStrength + characterIntelligence + characterDexterity;
                        return characterTotal;
                    }

};
#endif

---

//Orc.cpp
#include "Orc.h"
Orc::Orc()
{
//ctor
}

Orc::~Orc()
{
//dtor
}

Answer 1

您需要编译所有您的源文件(不是头文件)并将它们链接在一起。此时，最直接的方法是在一个命令中指定所有文件名:

g++ maingame.cpp character.cpp human.cpp orc.cpp

大型项目通常会单独编译每个文件，然后链接生成的.o(目标)文件，但您似乎还没有做到这一点。