What is causing my error? I am trying to create a player class and store a players name as a variable

Question

another noob here, so I hope someone with a bit of sense can help me! As my question states, I am simply trying to create a player class (it is for an RPG game). However, I have tried multiple ways of doing this, with the code shown being the latest, however I keep coming across different errors. I am using Microsoft visual c++ 2010 express and the error that I am currently facing is:

1>player.obj : error LNK2001: unresolved external symbol "private: static class std::basic_string,class std::allocator > Player::m_playerName" (?m_playerName@Player@@0V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@A)

I hope this is enough detail! The rest of the code/files I have created are as follows:

game.cpp

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

using namespace std;



int main() 
{

    Player main;


   main.setStats(); 
   main.showStats();


    int stopper;
   cin >> stopper;

    return 0;



}

player.h

#include <string>

class Player
    {
    public:

        Player();
        void showStats();
        void setStats();        


    private: 

         int m_playerLVL;
         static std::string m_playerName;
    };

player.cpp

#include "player.h"
#include <iostream>
#include <string>

using namespace std; 

Player::Player()
{
    cout << "Please enter your name: ";
    string playerName;
    getline (cin, playerName);
    m_playerName = playerName;
}

    void Player::showStats()
    {
        cout << "Hello, i am " << m_playerName << "and i am lvl " << m_playerLVL; 
    }

    void Player::setStats()
    {
        m_playerLVL = 1;
    }

Answer 1

You are declaring the name of the player to be static:

static std::string m_playerName; // DON'T MAKE IT STATIC!

That's semantically incorrect, and removing static happens to solve your problem. Each instance of Player should associate a different value to m_playerName (because each player has their own name). Declaring a data member static makes it global for the whole Player class (i.e. it is not given a per-instance value, but one global value which is the same for all Player objects). That doesn't sound like something you would want.

---

Now if for any reason you really meant to declare this as a static data member, then you should provide a definition for it at the global namespace scope:

std::string Player::m_playerName;

The linker is complaining about the lack of such a definition.