C++ error : undefined reference to class:functoin()

I am getting an error while compiling this program . This is a simple game made in c++.
Game-content---- the player(user) will attack and reduce power of the enemy and in turn the enemy will attack automatically and reduce power of player. I am not understanding what that error means.It would be generous of you if you answer to this question.

HERE IS THE CODE

main.cpp

 #include <iostream>
 #include "Player.h"
 using namespace std;
 int getattack(int choice);
 int enemypts = 200;
 int playerpts = 200;
 Player playerObj;
int main()
{
    int attack;
    attack = getattack(attack);
    while(attack !=4){
        switch(attack){
            case 1:playerObj.PlayerAttack(enemypts,playerpts);break;
            case 2:playerObj.PlayerAttack(enemypts,playerpts);break;
            case 3:playerObj.PlayerAttack(enemypts,playerpts);break;
            default :cout<<"  what was that ? do it again..... "<<endl;
             getattack(attack);break;
        }
        cout<<"  YOUR TURN -"<<endl;
        cin>>attack;
    }

    return 0;
}
int getattack(int choice){                                                             //get attack

    cout<<"  1 for hammer\n";
    cout<<"  2 for AK-47\n";
    cout<<"  3 for Space-12\n";
    cout<<"  4 to quit\n\n";
    cout<<"  YOUR TURN "<<endl;
    cin>>choice;

    return choice;
}

enemy.cpp

#include "enemy.h"
#include "Player.h"
#include "enemy.h"
#include<iostream>
#include<stdlib.h>
#include<time.h>
using namespace std;


enemy::enemy()
{

}

void enemy::enemyAttack(int p){
    int r;
    cout<<"  ENEMY'S TURN "<<endl;
    srand(time(0));
    r = rand()%100;
    p = p - r;
    cout<<"  Now its enemy's turn to attack"<<endl;
    cout<<"  The attack was of power "<<r<<endl;
    cout<<"  Player - remaining power "<<p<<endl;
}

player.cpp

#include "Player.h"
#include "enemy.h"
#include<iostream>
#include<cstdlib>
#include<time.h>
using namespace std;


enemy enemyObj;
Player::Player()
{

}

void PlayerAttack(int enpts,int plypts){
    int r;
    srand(time(0));
    r = rand()%100;
    enpts = enpts - r;
    cout<<"  Your attack was of power - "<<r<<endl;
    cout<<"  Enemy- remaining power : "<<enpts;
    enemyObj.enemyAttack(plypts);
}

just for sake of rechecking below.. enemy.h

#ifndef ENEMY_H
#define ENEMY_H

class enemy
{
    public:
        enemy();
        void enemyAttack(int p);
    private:
        int p;

};

#endif // ENEMY_H

player.h

#ifndef PLAYER_H
#define PLAYER_H


class Player
{
    public:
        Player();
        void PlayerAttack(int enpts,int plypts);
    private:
        int enpts,plypts;

};

#endif // PLAYER_H