Не работает extern для vector

extern vector<Card> CardList

for( int i = 0; i < CARDCOUNT; i++ ){
 
    Card element = ...
 
    CardList.push_back(element);
 
};

#include <iostream>
#include <cstdlib>
#include <vector>
#include "Game.h"
#include "Player.h"
#include "Card.h"
 
using namespace std;
 
 
extern const int CARDCOUNT = 8;
 
extern vector<Card> CardList;
 
 
//Game constructor
Game::Game(){
 
    //Card description
    struct cardData{
        int id;
        string type;
        string name;
        int value;
        string icon;
    };
 
    //Predefine cards like array of structure
    cardData cardDataDescription[] = {
        {0, "pika", "", 6, "♦"},
        {1, "cherva", "", 6, "♦"},
        {2, "buba", "", 6, "♦"},
        {3, "trefa", "", 6, "♦"},
 
        {4, "pika", "", 7, "♦"},
        {5, "cherva", "", 7, "♣"},
        {6, "buba", "", 7, "♥"},
        {7, "trefa", "", 7, "â™*"}
    };
 
    //Fill container by cards
    for( int i = 0; i < CARDCOUNT; i++ ){
        Card element(
            cardDataDescription[i].id,
            cardDataDescription[i].type,
            cardDataDescription[i].name,
            cardDataDescription[i].value,
            cardDataDescription[i].icon
        );
        CardList.push_back(element);
    };
 
    //Start game logic
    startGame();
}
 
 
/**
 * Get card from object
 * @param id Index of card object
 * @return object Card object
 */
Card Game::getCardById(int id){
    return CardList.at(id);
};
 
 
/**
 * Remove Card from vector container
 * @param id Id of removing object
 */
void Game::removeCardById(int id){
    CardList.erase(CardList.begin() + (id - 1));
};
 
 
/**
 * Clear screen
 */
void Game::clearWin(){
    cout << "\33[2J";
};