为什么我不断收到错误消息：“未定义对 'robots::robots()' 的引用

Question

我正在创建一个程序来练习我对类和文件的了解，但我可以让它发挥作用。以前我收到一个错误，说 robots::robots() 被定义了多次，但现在我有这个错误，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;
};

这里是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();
}

有人能找出我为什么不断收到此错误吗？

Answer 1

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

g++ main.cpp enemy_definitions.cpp

这应该正确链接您的代码。