So I have made a simple class, Newplayer where you can set the name and get the name. Code works when the class is in one cpp file, but as soon as I split the class into an .h and .cpp file I get compiler error which says is unreference.

Text_adventure/main.cpp:14: undefined reference to `Newplayer::setName(std::string)'

In the player.h

#pragma once
#include <stdio.h>
#include <iostream>
#include <fstream>
#include <string>

class Newplayer
{
private:
std::string m_name;

public:

void setName(std::string cName);
std::string getName();
};

int the player.cpp

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

    void Newplayer::setName(std::string cName)
    {
        m_name = cName;
    }
    
    std::string Newplayer::getName()
    { 
        return m_name;
    }

The main file

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



int main()
{
    // check if a file exist
    //load file xor exit
    Newplayer player1;
    player1.setName("Stackoverflow");
    
    
    

    
    
    return 0;
}

I don't understand why I am getting an error to string type; everything works when I make a single main.cpp file containing all the files, no warnings.

#include <stdio.h>
#include <iostream>
#include <fstream>
#include <string>

class Newplayer
{
    
    std::string m_name;

    
    public:
    
    void setName(std::string cName)
    {

    m_name = cName;
    }

    
    std::string getName()
    { 
        return m_name;
    }
    

};


int main()
{

    Newplayer player1;

    
    player1.setName("Stackoverflow");

   printf("Your name is : %s \n", player1.getName().c_str());
 
    
    return 0;
}

COMPILER INFO

I am running this compiler as of now, I saw that there were some issues with GCC 5, but I don't think I am running GCC 5, or maybe I am, I am clueless on this.

(base) Ivan@ivan-ThinkPad-T490:/usr/bin$ dpkg --list | grep compiler
ii  g++                                        4:9.3.0-1ubuntu2                      amd64        GNU C++ compiler
ii  g++-9                                      9.3.0-17ubuntu1~20.04                 amd64        GNU C++ compiler
ii  gcc                                        4:9.3.0-1ubuntu2                      amd64        GNU C compiler
ii  gcc-9                                      9.3.0-17ubuntu1~20.04