C++ Struct function body calling another structs function, same module

Question

I am attempting to make a Chess module using a ChessPiece struct and a ChessGame struct. Using XCode 6.1.1. Here is my header file and function in question in my Chess.cpp. I get the error, "Use of undeclared identifier 'initChessPiece' did you mean 'ChessPiece::initChessPiece'?. If I make that change it says the error, 'call to non-stack member function without an object argument.' Finally, if I make the line,

game.pieces[i].initChessPiece(game.pieces[i], color, piece, x, y);

Linker throws the error:

Undefined symbols for architecture x86_64: "ChessPiece::initChessPiece(ChessPiece, std::__1::basic_string, std::__1::allocator > const&, std::__1::basic_string, std::__1::allocator > const&, unsigned int, unsigned int)", referenced from: readChessGame(ChessGame&, std::__1::basic_string, std::__1::allocator > const&) in Chess.o ld: symbol(s) not found for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation)

#ifndef CHESS_H
#define CHESS_H

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

using namespace std;

const int ROWS = 8;
const int COLUMNS = 8;

struct ChessPiece {

string name;
string colour;
unsigned int row;
unsigned int column;
void initChessPiece(ChessPiece, const string& colour, const string& name, unsigned int row, unsigned int column);
string getStringColourChessPiece(const ChessPiece&) const;
string getStringNameChessPiece(const ChessPiece&) const;

friend class ChessGame;
};

struct ChessGame {
unsigned int chessBoard[ROWS][COLUMNS];
ChessPiece pieces[32];

void readChessGame(ChessGame&, const string& filename);
void printChessGame(const ChessGame&);
int scoreChessGame(const ChessGame&) const;
bool isFinished(const ChessGame&) const;
};


#endif

Chess.cpp

#include "Chess.h"
void readChessGame(ChessGame& game, const string& filename) {

ifstream inData;
inData.open(filename.c_str());

string color;
string piece;
unsigned int x;
unsigned int y;
for (int i=0;i<32;i++) {
    inData >> color >> piece >> x >> y;
    initChessPiece(game.pieces[i], color, piece, x, y);
}
}

void initChessPiece(ChessPiece& piece, const string& colour, const string& name, unsigned int row, unsigned int column) {
piece.row = row;
piece.column = column;
piece.name = name;
piece.colour = colour;
}

This is my CS final practice question and the all the function headers were set by the instructions so I need to work with the way they are setup

Answer 1

You need an object of type ChessPiece to be able to call initChessPiece().

Something like this:

#include "Chess.h"
void readChessGame(ChessGame& game, const string& filename) {

    ifstream inData;
    inData.open(filename.c_str());

    string color;
    string piece;
    unsigned int x;
    unsigned int y;
    for (int i=0;i<32;i++) {
        inData >> color >> piece >> x >> y;
        game.pieces[i].initChessPiece(game.pieces[i], color, piece, x, y);
    }
}

You should probably remove the piece parameter since you will have the object available in the function through the this pointer. If you decide to keep it you need to make it a reference or a pointer to be able to change the value of the pieces in your array.

 game.pieces[i].initChessPiece(color, piece, x, y);

EDIT2: void ChessPiece::initChessPiece(const string& colour, const string& name, unsigned int row, unsigned int column) { this->name = name; this->colour = colour; this->row = row; this->column = column; }

I think you should also consider making this a constructor.

Edit: If you want to keep your calling style you could make the initChessPiece() static. Then it should be callable without an object.