Проблема C ++ с LNK 2001 - Частные статические переменные

Question

Я знаю, что существуют очень похожие вопросы.Однако я попытался определить эти переменные в моем файле .cpp (даже создавая пространство имен для проекта и пытаясь таким образом определить переменные в том же пространстве имен), и я все еще получаю ошибку LNK2001: Unresolved external symbol.Вот соответствующие части моего кода:

Word.h

#pragma once

#include <string>
#include <vector>


namespace GTW 
{

    class Word
    {
    private:
        std::string word;
        std::string scrambledWord;
        static unsigned int numWords;
        static std::vector<std::string> allWords;   // A vector to store all the words in
        static std::vector<std::string> usedWords;  // Stores the words already used

        void ScrambleWord();
        template<typename _T>
        bool vecContains(std::vector<_T>& checkVec, _T& element) const;
        static int RandomNumber(unsigned int startNum, unsigned int endNum);

    public:
        Word();

        /* GETTERS */
        std::string getWord() const;
        std::string getScrambledWord() const;
        unsigned int getNumWords() const;
        std::vector<std::string> getAllWords() const;
    };

}

Word.cpp

#include <iostream>
#include <fstream>
#include <algorithm>
#include <string>
#include <vector>
#include <random>
#include "Word.h"

using namespace std;

namespace GTW 
{
    /* This is my attempt at defining the static variables */
    unsigned int Word::numWords;
    vector<string> Word::allWords;
    vector<string> Word::usedWords;


    void Word::ScrambleWord()
    {
        // Scrambles word by setting this->scrambledWord

        return;
    }


    template<typename _T>
    bool Word::vecContains(vector<_T>& checkVec, _T& element) const
    {
        typename vector<_T>::iterator it;

        it = find(checkVec.begin(), checkVec.end(), element);

        if (it != checkVec.end()) { return true; }
        else { return false; }
    }


    int Word::RandomNumber(unsigned int startNum, unsigned int endNum)
    {
        // Returns random number
    }


    Word::Word()
    {
        if (Word::allWords.empty())  // Makes sure vector is only filled once
        {
            // Reads a bunch of Word::allWords from a file into the "Word::allWords" vector
            ifstream wordList("words.dat");
            if (wordList.is_open())
            {
                while (getline(wordList, word)) { Word::allWords.push_back(word); }
                wordList.close();
            }
        }

        // Stores the number of Word::allWords in the vector
        Word::numWords = static_cast<int>(Word::allWords.size());
        int randNum = 0;

        // Starts a loop that will repeat if the new word has already been used
        do
        {
            // Value for random index
            randNum = RandomNumber(0, Word::numWords - 1);

            // Sets word to a random index in the vector "Word::allWords"
            word = Word::allWords.at(randNum);
        } while (vecContains<string>(Word::usedWords, word));

        // Scrambles the word
        ScrambleWord();

        // Adds "word" to Word::usedWords vector
        Word::usedWords.push_back(word);
    }

    /* GETTERS */
    string Word::getWord() const { return word; }
    string Word::getScrambledWord() const { return scrambledWord; }
    unsigned int Word::getNumWords() const { return Word::numWords; }
    vector<string> Word::getAllWords() const { return Word::allWords; }

}

Полное сообщение об ошибке:

1>Word.obj : error LNK2001: unresolved external symbol "private: static unsigned int Word::numWords" (?numWords@Word@@0IA)
1>Word.obj : error LNK2001: unresolved external symbol "private: static class std::vector<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,class std::allocator<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > > > Word::allWords" (?allWords@Word@@0V?$vector@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@V?$allocator@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@2@@std@@A)
1>Word.obj : error LNK2001: unresolved external symbol "private: static class std::vector<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,class std::allocator<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > > > Word::usedWords" (?usedWords@Word@@0V?$vector@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@V?$allocator@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@2@@std@@A)
1>C:\Users\username\Dev\GuessTheWord\bin\Debug-x64\GuessTheWord\GuessTheWord.exe : fatal error LNK1120: 3 unresolved externals
1>Done building project "GuessTheWord.vcxproj" -- FAILED.