c++ - 使用接口(interface)时对 vtable 的 undefined reference

Question

我环顾四周，但我不太清楚哪里出了问题，因为我在使用接口(interface)时似乎遵循了正确的约定，但也许我忽略了一些东西。我得到的确切错误是:

undefined reference to `vtable for Icommand'

我才刚刚开始将我的类和类声明分离到单独的头文件中，所以我可能在某处缺少预处理器指令。

ma​​in.cpp:

#include <iostream>
#include <string>
#include <cstdlib>
#include "Icommand.h"

#include "Command.h"

using namespace std;

void pause();

int main(){


    Icommand *run = new Command("TEST");
    cout << run->getCommand() << endl;
    delete run;

    pause();
}

void pause(){
    cin.clear();
    cin.ignore(cin.rdbuf()->in_avail());
    cin.get();
}

Icommand.h:

#ifndef ICOMMAND_H
#define ICOMMAND_H

#include <string>
#include <vector>


class Icommand
{
    private:

    public:
        Icommand(){}
        virtual ~Icommand(){}
        virtual bool run(std::string object1) = 0;
        virtual bool run(std::string object1, std::string object2) = 0;
        virtual std::string getCommand() const;
};



#endif // ICOMMAND_H

Command.h:

#ifndef COMMAND_H
#define COMMAND_H

#include <string>
#include <vector>

#include "Icommand.h"

class Command : public Icommand {

    private:
        std::string command;
        std::vector<std::string> synonymns;
        Command(); // private so class much be instantiated with a command

    public:
        Command(std::string command) : command(command){}
        ~Command(){}
        bool run(std::string object1);
        bool run(std::string object1, std::string object2);
        std::string getCommand() const;


};
#endif // COMMAND_H

命令.cpp:

#include <string>
#include <vector>

#include "Command.h"

bool Command::run(std::string object1){
    return false;
}
bool Command::run(std::string object1, std::string object2){
    return false;
}
std::string Command::getCommand() const {return command;}

Answer 1

在Icommand.h中，替换

virtual std::string getCommand() const;

与

virtual std::string getCommand() const = 0;

使其成为纯虚拟的。然后编译器可以为 Icommand 生成一个 vtable。或者，实现 Icommand::getCommand。