2D array of a class object call by reference - c++

Question

I searched a lot on stackoverflow and google but nothing as my case. I want to declare a 2d array of my class box. It works normal, then i need a print function for it. If i printed the array inside main(), it was fine but now with a printer function i seem to get a lot of errors. Please help me with my mistake.
#include <iostream>
class box
{
private:
char life;
public:
box();
void display();
void input_alive();
void input_dead();
};
box::box()
{
life = '0';
}
void box::display()
{
std::cout << " " <<life <<" ";
}
void box::input_alive()
{
life = '1';
}
void box::input_dead()
{
life = '0';
}
void printer(box *array, int yy, int xx)
{
int i, j;
for(i=0; i<yy; i++) //PRINTER
{
for(j=0; j<xx; j++)
{
array[i][j].display();
if (j+1 == xx) //just newline for separate rows
std::cout << std::endl;
}
}
}
int main()
{
int row=5, col=5;
box arr[row][col];
arr[3][4].input_alive();
arr[1][1].input_alive();
printer(arr, row, col);
return 0;
}
this syntax of passing array by reference works fine in normal int/char arrays, but why not here. If i put printer function in main, it works fine :(. Do i have to use new or what? or how do i pass box array into function? thanks.

Answer 1

First of all, C++ doesn't support variable length arrays, so your code is not standards compliant and therefore is not portable.
Second, you can avoid all the pain by using std::array:
#include <array>
template <size_t ROWS, size_t COLS>
void printer(std::array<box, ROWS>, COLS>& arr)
{
for(int i=0; i<ROW; ++i)
{
for(int j=0; j<COL; ++j)
{
// do something with arr[i][j]
}
}
int main()
{
const int row=5;
const int col=5;
std::array<std::array<box, row>, col> arr;
arr[3][4].input_alive();
arr[1][1].input_alive();
printer(arr);
return 0;
}

Answer 2

Your solution is to forget about raw arrays. Instead, you use std::vector or std::array and write a Matrix class with operator(), as explained in the C++ FAQ. See also the next item in the FAQ for reasons why you'd want to prefer the (x, y) form to [x][y], but consider that there are good programmers who prefer the latter syntax (using a proxy class), so the case is perhaps not as clear as the FAQ says it is.
In any case, you need a Matrix class with a std::vector or std::array implementation. Raw arrays are the wrong tool for this task.