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Trouble with accessing friend

Yoshima (20)
Hello,
I'm trying to make a simple tic-tac-toe game and am having trouble with using 'friend'. During the computer's move I want the computer's class to access and modify the board array in the 'Gameboard' class.

I have declared the 'Computer' class a 'friend' in the 'Gameboard' header. However on compile a number of errors occur:

In computer cpp:
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line 27 'board' was not declared in this scope
line 28 invalid use of member (did you forget the '&'?)
line 35 'board' has not been declared
line 35 Prototype for 'bool Computer::validateMove(int, char, char, int)' does not match any class in computer
line 41'board' was not declared in this scope


I've spent ages renaming and rearranging code but I'm guessing that there's a fundamental concept I'm missing. Any help would be great thanks.

Computer header.
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#ifndef COMPUTER_H
#define COMPUTER_H

#include "Gameboard.h"

class Computer
{
public:
	Computer(char);
	void print();
	char compMove(char, char);
private: 
	char piece;
	char move;
	int sqr;
	bool validateMove(int, char, char, Gameboard board);
};

#endif


Computer cpp

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#include <iostream>
#include <string>
#include <time.h>

using namespace std;

#include "Computer.h"

Computer::Computer(char compPiece)
{
	piece = compPiece;
	srand(time(0));

}

void Computer::print()
{
	cout << "\nOk CPU... so this works" << endl;
}

char Computer::compMove(char x, char o)
{
	do
	{
		sqr = (rand()%9)+1;
		move = '0'+sqr;
		validateMove(move,x,o,board);
	}while(validateMove == false);
	
	cout << "computer to move to: " << move << endl;
	return move;

}

bool Computer::validateMove(int move, char xCk, char oCk, board)
{
	for(int i = 0; i < 3; i++)
	{
		for(int j = 0; j < 3; j++)
		{
			if((board[i][j] == xCk) || (board[i][j] == oCk))
			{
				return false;
			}
			else 
			{
				return true;
			}
		}
	}

}


Gameboard header.

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#ifndef GAMEBOARD_H
#define GAMEBOARD_H

class Gameboard
{
	friend class Computer;
public:
	Gameboard();
	void printBoard();
	void makeMove(char, char);
private:
	char board[3][3];
	
};

#endif


Gameboard cpp.

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#include <iostream>
#include <string>

using namespace std;

#include "Gameboard.h"

Gameboard::Gameboard()
{
	int k = 1;
	for(int i = 0; i < 3; i++)
	{
		for(int j = 0; j < 3; j++)
		{
			char setNum = '0' + (j+k);
			board[i][j] = setNum;
		}
		k+=3;	
	}
}
		
void Gameboard::printBoard()
{
	cout << "\t-------------\n";
	cout << "\t| "<<board[0][0]<<" | "<<board[0][1]<<" | "<<board[0][2]<<" |\n";
	cout << "\t|---|---|---|\n";
	cout << "\t| "<<board[1][0]<<" | "<<board[1][1]<<" | "<<board[1][2]<<" |\n";
	cout << "\t|---|---|---|\n";
	cout << "\t| "<<board[2][0]<<" | "<<board[2][1]<<" | "<<board[2][2]<<" |\n";
	cout << "\t-------------\n"<< endl;
}

void Gameboard::makeMove(char move, char piece)
{
	
	for(int i = 0; i < 3; i++)
	{
		for(int j = 0; j < 3; j++)
		{
			if(board[i][j] == move)
			{
				board[i][j] = piece;
			}
		}
	}
	
}


Main.

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#include <iostream>
#include <string>
#include <cctype>

#include "Player.h"
#include "Computer.h"
#include "Gameboard.h"

using namespace std;

const char x = 'X';
const char o = 'O';
const char noOne = 'N';
const char tie = 'T';
void const instructions();
void pieceAsk();
char onePiece;
char compPiece;
char turn;
char winner;
char thisMove;
char test;


int main() 
{

	Gameboard boardObj;
    instructions();
	boardObj.printBoard();
	pieceAsk();
	Player playerOne(onePiece);
	Computer comp(compPiece);
	winner = noOne;
	turn = x;
	
	while(winner == noOne)
	{
	
		if(turn == onePiece)
		{
			playerOne.print();
			//thisMove = playerOne.playerMove();
			boardObj.makeMove(playerOne.playerMove(), onePiece);
			boardObj.printBoard();
			turn = compPiece;

			
		}
		else if(turn == compPiece)
		{
			boardObj.makeMove(comp.compMove(x,o), compPiece);
			boardObj.printBoard();
			turn = onePiece;
		}
		else
		{
			printf("Something's gone wrong");
		}
	}
	
    return 0;
}

void const instructions()
{
	cout << "\nXOXOXOX Noughts and Crosses Extreme XOXOXOX" << endl;
	cout << "\nRules: Match three in a row vertically, horizontally or diagonally\n"<<endl;
}

void pieceAsk()
{
	char choice;
	cout << "Would you like to be Os or Xs (Enter O or X): ";
	cin >> choice;
	
	while((choice != o) && (choice != x))
	{
		cout << "Please enter a valid answer (X or O): ";
		cin >> choice;
	}
		
	if(choice == x)
	{
		cout << "\nYou will play as X's\n";
		onePiece = x;
		compPiece = o;
	}
	else if(choice == o)
	{
		cout << "\nYou will play as O's\n";
		onePiece = o;
		compPiece = x;
	}
	else
	{
		cout << "\nERROR. DEFAULT SETTING: You will play as X's\n";
		onePiece = x;
		compPiece = o;
	}
}



hamsterman (4538)
line 27: when you make class A a friend of class B, A can access private members of B object. You do need to have a B class object. board is a member of GameBoard class. You cannot access it without a GameBoard object. The right way would be my_board.board. You could either make boardObj a global variable (not suggested) or add a GameBoard& to Computer class.

line 28: validateMove is a function, not a variable. The right way would be }while(validateMove(/*some arguments*/) == false);

line 35: when you put something in argument list you must specify its class (GameBoard in this case)
line 35: since compiler couldn't understand your arguments it cannot find appropriate function declared in Computer class and complains about it.

line 41: this is caused by errors on line 35. I can't say what is the compiler thinking though..
Last edited on
Yoshima (20)
Thanks for the reply... your suggestion fixed the 'validateMove' problem...

I'm still unsure on the 'friend' problem...

I've changed a few functions and tried to use the boardObj as an argument in the compMove function.

In 'main' I changed
boardObj.makeMove(comp.compMove(x,o), compPiece);
to
boardObj.makeMove(comp.compMove(x,o,boardObj), compPiece);

I now only get the following error on lines 7 and 8 in the Computer cpp code that follows:
No matching function for call to 'Computer::validateMove(char&,char&, char&, char[3][3])'

What needs to be done to fix this? Thanks.


Computer header

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#ifndef COMPUTER_H
#define COMPUTER_H

#include "Gameboard.h"

class Computer
{
public:
	Computer(char);
	void print();
	char compMove(char, char, Gameboard &boardSet);
private: 
	char piece;
	char move;
	int sqr;
	bool validateMove(int, char, char, Gameboard &board);
};

#endif


Computer cpp

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char Computer::compMove(char x, char o, Gameboard &boardSet)
{
	do
	{
		sqr = (rand()%9)+1;
		move = '0'+sqr;
		validateMove(move,x,o,boardSet.board);
	}while(validateMove(move,x,o,boardSet.board) == false);
	
	cout << "computer to move to: " << move << endl;
	return move;

}

bool Computer::validateMove(int move, char xCk, char oCk,Gameboard& boardSet)
{
	for(int i = 0; i < 3; i++)
	{
		for(int j = 0; j < 3; j++)
		{
			if((boardSet.board[i][j] == xCk) || (boardSet.board[i][j] == oCk))
			{
				return false;
			}
			else 
			{
				return true;
			}
		}
	}
}

Last edited on
hamsterman (4538)
This is because function expects Gameboard object, you give it Gameboard::board which is char[3][3]. Just change 'boardSet.board' to 'boardSet' since you want to pass the whole object and not only its member.

Nore: line 7 is useless. You're just calling the same function twice..
Yoshima (20)
Cool... that works...

Thanks a lot hamsterman...
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