C++ printing 2d array

Question

Im trying to make this CommandLine based game called "DungeonCrawl" in ObjectOrientedProgramming... I have created a header & source file, then I have declared functions and the class in header file, and definitions are on the source file.

The problem: When I print the board using 2 for loops, in a Void function, it prints some random integers instead of just 0's...

Result after printing:

0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 0 0 
0 0 0 0 0 0 0 0 1303831201 100681557 
1606416496 32767 17 0 1 0 104 1 1606581343 32767 
1606416256 32767 1606423158 32767 1606416280 32767 1606416280 32767 1 0 
1606416304 32767 0 1 0 0 1606416320 32767 0 0 
0 0 0 0 0 0 0 0 1606416288 32767

This is the header file:

#ifndef dungeoncrawl_hpp
#define dungeoncrawl_hpp
#include <iostream>
#include <stdio.h>

using namespace std;

class dungeoncrawl {
public:
    dungeoncrawl();
    void drawBoard();
    ~dungeoncrawl();
private:
    int board[10][10];
    uint8_t player_pos[0][0], enemy_pos[0][0];

};

#endif /* dungeoncrawl_hpp */

and here's the source file:

#include "dungeoncrawl.hpp"

// Constructor
class dungeoncrawl::dungeoncrawl {
    int board[10][10] = {
        {0,0,0,0,0,0,0,0,0,0},
        {0,0,0,0,0,0,0,0,0,0},
        {0,0,0,0,0,0,0,0,0,0},
        {0,0,0,0,0,0,0,0,0,0},
        {0,0,0,0,0,0,0,0,0,0},
        {0,0,0,0,0,0,0,0,0,0},
        {0,0,0,0,0,0,0,0,0,0},
        {0,0,0,0,0,0,0,0,0,0},
        {0,0,0,0,0,0,0,0,0,0},
        {0,0,0,0,0,0,0,0,0,0}
    };
};

// Con-&-Destructor
dungeoncrawl::dungeoncrawl(){}
dungeoncrawl::~dungeoncrawl(){}

void dungeoncrawl::drawBoard(){
    for(int i = 0; i < 10; i++){
        for(int j = 0; j < 10; j++){
            cout << board[i][j] << " ";
        }
        cout << endl;
    }
};

`int board[10][10]` that you declare and initialize in `dungeoncrawl` constructor is a local variable, completely unrelated to `this->board` member variable, which itself is never initialized and contains random garbage. — Igor Tandetnik, Dec 20 '16 at 15:24
You're shadowing your own variable there and failing to initialize the real one. If you used a simple 100-element `std::vector` your code would be a lot more C++ and you could actually get initialization for free. — tadman, Dec 20 '16 at 15:25
`// Constructor` `class dungeoncrawl::dungeoncrawl` - No, I don't think so. — IInspectable, Dec 20 '16 at 15:32
Also note that `player_pos` and `enemy_pos` are both zero-sized arrays. I don't remember whether they're legal C++, but even if they are you won't do much with them. — Quentin, Dec 20 '16 at 15:33
I think you need to get a few books from [The Definitive C++ Book Guide and List](http://stackoverflow.com/q/388242/1889329). Stack Overflow isn't the appropriate place to ask for guidance on getting the basics straight. — IInspectable, Dec 20 '16 at 15:35

score 1 · Accepted Answer · answered Dec 20 '16 at 16:17

There are two errors in your code. At first:

uint8_t player_pos[0][0], enemy_pos[0][0];

Zero length arrays are offered by gcc as an extension. It is useless in your case.

Secondly:

class dungeoncrawl::dungeoncrawl {

It is not a construstor. If you want to initialize class member you can do it in a constructor. Such as here:

// Constructor
dungeoncrawl::dungeoncrawl(){
    for(int i = 0; i < 10; i++){
        for(int j = 0; j < 10; j++){
            board[i][j] = 0;
        }
    }
}

Or, for example you can declare the array as static:

//dungeoncrawl.hpp
private:        
     static int board[10][10];

//dungeoncrawl.cpp
int dungeoncrawl::board[10][10] = {
                  {0,0,0,0,0,0,0,0,0,0},
                  {0,0,0,0,0,0,0,0,0,0},
                  {0,0,0,0,0,0,0,0,0,0},
                  {0,0,0,0,0,0,0,0,0,0},
                  {0,0,0,0,0,0,0,0,0,0},
                  {0,0,0,0,0,0,0,0,0,0},
                  {0,0,0,0,0,0,0,0,0,0},
                  {0,0,0,0,0,0,0,0,0,0},
                  {0,0,0,0,0,0,0,0,0,0},
                  {0,0,0,0,0,0,0,0,0,0}
};

C++ printing 2d array

1 Answers1