Duplicate error, help needed

[Prummi]

I am making a little command line game and I can't seem to fix this weird error. It says duplicate error of my objects, but I am using #pragma once

The full error:
duplicate symbol _GameState in:
/Users/prummi/Library/Developer/Xcode/DerivedData/Mastermind-fottybxidepfogekmopuyksleerv/Build/Intermediates.noindex/Mastermind.build/Debug/Mastermind.build/Objects-normal/x86_64/main.o
/Users/prummi/Library/Developer/Xcode/DerivedData/Mastermind-fottybxidepfogekmopuyksleerv/Build/Intermediates.noindex/Mastermind.build/Debug/Mastermind.build/Objects-normal/x86_64/StateMachine.o
duplicate symbol _Statemachine in:
/Users/prummi/Library/Developer/Xcode/DerivedData/Mastermind-fottybxidepfogekmopuyksleerv/Build/Intermediates.noindex/Mastermind.build/Debug/Mastermind.build/Objects-normal/x86_64/main.o
/Users/prummi/Library/Developer/Xcode/DerivedData/Mastermind-fottybxidepfogekmopuyksleerv/Build/Intermediates.noindex/Mastermind.build/Debug/Mastermind.build/Objects-normal/x86_64/StateMachine.o
duplicate symbol _myCode in:
/Users/prummi/Library/Developer/Xcode/DerivedData/Mastermind-fottybxidepfogekmopuyksleerv/Build/Intermediates.noindex/Mastermind.build/Debug/Mastermind.build/Objects-normal/x86_64/main.o
/Users/prummi/Library/Developer/Xcode/DerivedData/Mastermind-fottybxidepfogekmopuyksleerv/Build/Intermediates.noindex/Mastermind.build/Debug/Mastermind.build/Objects-normal/x86_64/StateMachine.o
ld: 3 duplicate symbols for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

main.cpp

  #include "Code.hpp"
#include "StateMachine.hpp"
#include "ObjectDeclerations.hpp"

int main() {
    
    
    GameState = GameStates::INTRO; // make the GameState intro so the program starts with intro
    
    switch ( GameState ) // handle the different game states
    {
        case GameStates::INTRO:
            Statemachine.processIntro();
            
        case GameStates::MAIN_MENU:
            Statemachine.processMainMenu();
            
        case GameStates::PLAYING:
            Statemachine.processPlaying();
            
        case GameStates::CODECRACKED:
            Statemachine.proccesCodeCracked();
            
        case GameStates::EXIT:
            Statemachine.processExit();
            break;
        
    }
}




ObjectDeclerations.hpp

#pragma once

Statemachine Statemachine; // Create Statemachine object containing the proccessing functions of the different states
Code myCode; // Create a code object containing the games code the user needs to crack

GameStates GameState; // Create enum object for the different gamestates




Code.cpp

void Code::printCode()
{
    std::cout << "The code is ";
    for ( int i = 0; i < 4; i++ )
    {
        std::cout << code[i] << " ";
    }
    std::cout << std::endl;
}

void Code::printGuess()
{
    std::cout << "The code guess is ";
    for ( int i = 0; i < 4; i++ )
    {
        std::cout << guess[i] << " ";
    }
    std::cout << std::endl;
}

void Code::generateCode()
{
    srand( static_cast<unsigned int>(time(NULL)) ); // initialise random seed
    for(int i = 0; i < 4; i++)
    {
        randomNumber = rand() % 6 + 1; // give the randomNumber variable a random number between 1 and 6
        code[i] = randomNumber;
    }
}

void Code::insertCode()
{
    for ( int i = 0; i < 4; )
    {
        std::cout << "Enter code number " << i + 1 << std::endl;
        std::cin >> code[i];
        if( code[i] > 0 && code[i] < 7 )
        {
            i++;
        }
        else
        {
            std::cout << "input invalid, try again" << std::endl;
        }
    }
}

void Code::insertGuess()
{
    for ( int i = 0; i < 4; )
    {
        std::cout << "Enter code number " << i + 1 << std::endl;
        std::cin >> guess[i];
        if( guess[i] > 0 && guess[i] < 7 )
        {
            i++;
        }
        else
        {
            std::cout << "input invalid, try again" << std::endl;
        }
    }
}

int Code::checkGuess()
{
    int goodGuesses = 0;
    
    for(int i = 0; i < 4; i++)
    {
        if ( code[i] == guess[i] )
        {
            goodGuesses++;
        }
    }
    
    return goodGuesses;
}




Code.hpp

#pragma once

class Code
{
public:
// variables
    int randomNumber;
private:
    int code[4]; // array containing the code numbers
    int guess[4]; // array containing the guesses of the code
public:
// functions
    void printCode();
    void generateCode();
    void insertCode();
    
    void insertGuess();
    void printGuess();
    
    int checkGuess();
};




StateMachine.cpp

#include <iostream>
#include "StateMachine.hpp"
#include "Code.hpp"
#include "ObjectDeclerations.hpp"

// intro
void Statemachine::processIntro()
{
    std::cout << "Welcome to mastermind!" << std::endl;
    std::cout << "The point in this game is to guess the code, containing 4 numbers of 1 to 6." << std::endl;
    std::cout << "After every guess you will be told how many numbers were correct" << std::endl;
    std::cout << "" << std::endl;
}

// main menu
void Statemachine::processMainMenu()
{
    std::cout << "MAIN MENU:" << std::endl;
    mainMenu = true; // set mainMenu to true to enter the main menu loop
    
    while(mainMenu) // enter main menu loop
    {
        std::cout << "Enter 1 to generate a random code" << std::endl;
        std::cout << "Enter 2 to put in a code yourself" << std::endl;
        std::cin >> mainMenuChoice;
        
        switch (mainMenuChoice)
        {
            case 1:
                myCode.generateCode();
                std::cout << "Code set" << std::endl;
                mainMenu = false;
                break;
                
            case 2:
                // insert a code
                myCode.insertCode();
                std::cout << "Code set" << std::endl;
                mainMenu = false;
                break;
                
            default:
                std::cout << "Choice invalid, try again" << std::endl;
                break;
        }
    }
}

// playing
void Statemachine::processPlaying()
{
    std::cout << "Good luck cracking the code!" << std::endl << std::endl;
    attempt = 1;
    playing = true; // set playing to true to enter the playing loop
    while (playing)
    {
        std::cout << std::endl;
        std::cout << "Starting attempt number " << attempt << ":" << std::endl;
        myCode.insertGuess();
        myCode.printGuess();
        std::cout << "You had " << myCode.checkGuess() << " correct number(s)" << std::endl; // print how many numbers were guessed correct
        if (myCode.checkGuess() == 4)
        {
            playing = false;
        }
        attempt++;
    }
}

// code cracked
void Statemachine::proccesCodeCracked()
{
    std::cout << "Congratulations, you cracked the code!" << std::endl;
    std::cout << "This took you " << attempt << " attempts" << std::endl;
    GameState = GameStates::INTRO;
}


// exit
void Statemachine::processExit()
{
    std::cout << "" << std::endl;
    std::cout << "EXITING GAME" << std::endl;
}




StateMachine.hpp

#pragma once

enum class GameStates {INTRO, MAIN_MENU, PLAYING, CODECRACKED, EXIT}; // Create enum with gamestates

class Statemachine
{
public:
// Viarable declerations
    int mainMenuChoice;
    int attempt;
    bool mainMenu;
    bool playing;



// Function declerations
    void processIntro();
    void processMainMenu();
    void processPlaying();
    void processExit();
    void proccesCodeCracked();
};

Could anybody tell me how to fix this? Thanks!

[Peter87]

#pragma once only helps with preventing the same header file from being included more than once in the same translation unit. If you include ObjectDeclerations.hpp in multiple translation units the Statemachine, myCode and GameState objects will get defined multiple times which is not allowed.

If you want these global variables you need to declare them as extern in the header ...

ObjectDeclerations.hpp

extern Statemachine Statemachine;
extern Code myCode;
extern GameStates GameState;

... and then put the definitions in a source file instead.

ObjectDeclerations.cpp

Statemachine Statemachine;
Code myCode;
GameStates GameState;

If you're using C++17 another alternative is to make them inline.

ObjectDeclerations.hpp

inline Statemachine Statemachine;
inline Code myCode;
inline GameStates GameState;

Then you don't need to add anything extra to the source file.