Why do I keep getting the error: "undefined reference to 'robots::robots()'

Question

我正在创建一个程序来练习我在类和文件方面的知识，但我可以让它工作。以前我收到一条错误消息说 robots::robots() 被定义了多次，但现在我收到一条错误消息说未定义对 'robots::robots()' 的引用。这是 enemy_definitions.h 的代码：

#include <iostream>
using namespace std;

class enemies
{
    public:
    string name;
    int hp;
    int damage;
    virtual void print_information();
};

class robots: public enemies
{
    public:
        robots();
        void print_information();
    private:
        int power_requirement;
};

class zombies: public enemies
{
    public:
        void print_information();
    private:
        int height;
};

class aliens: public enemies
{
    public:
        void print_information();
    private:
        string colour;
};

这是 enemy_definitions.cpp 的代码：

#include <iostream>
#include "enemy_definitions.h"

void enemies :: print_information()
{
}

robots :: robots()
    {
        cout <<"Name: ";
        cin >> name;
        cout <<"\nhp: ";
        cin >> hp;
        cout <<"\ndamage: ";
        cin >> damage;
        cout <<"\n power_requirement: ";
        cin >> power_requirement;
    }

void robots :: print_information()
{
    cout << this->name << " has ";
    cout << this->hp << "hit-points, ";
    cout << this->damage << " damage and ";
    cout << this->power_requirement << "power requirement";
}

void zombies :: print_information()
{
    cout << this->name << " has ";
    cout << this->hp << "hit-points, ";
    cout << this->damage << " damage and ";
    cout << this->height << "height";
}

void aliens :: print_information()
{
    cout << this->name << " has ";
    cout << this->hp << "hit-points, ";
    cout << this->damage << " damage and ";
    cout << this->colour << "colour";
}

这里是 main.cpp 的代码：

#include <iostream>
#include "enemy_definitions.h"

using namespace std;

int main()
{
robots Bertha;
Bertha.print_information();
}

有人能找出为什么我总是收到这个错误吗？

Answer 1

您只是在编译 main.cpp 文件，这就是编译器无法 link 您的函数定义的原因。使用

g++ main.cpp enemy_definitions.cpp

这应该 link 您的代码正确。

Why do I keep getting the error: "undefined reference to 'robots::robots()'

Why do I keep getting the error: "undefined reference to 'robots::robots()'

c++

class

file

include