'this' cannot be used in a constant expression error (C++) - c++

Question

all. I have a class defined as follows:
class Board {
int columns, rows;
bool board[10][10];
public:
Board(int, int);
void nextFrame();
void printFrame();
};
My void nextFrame() keeps giving me errors for [rows][columns] because " 'this' cannot be in a constant expression" for both of them. How can I redefine this so that it works? I understand the error. The definition of the function is below, and the error occurs on the 3rd line of the following code sample.
void Board::nextFrame() {
int numSurrounding = 0;
bool tempBoard[rows][columns];
for (int i = 0; i < rows; i++)
{
for (int j = 0; j < columns; j++)
{
if ((i + 1) < rows && board[i + 1][j] == true)
{
numSurrounding++;
}
if ((i - 1) >= 0 && board[i - 1][j] == true)
{
numSurrounding++;
}
if ((j + 1) < columns && board[i][j + 1] == true)
{
numSurrounding++;
}
if ((j - 1) >= 0 && board[i][j - 1] == true)
{
numSurrounding++;
}
if ((i + 1) < rows && (j + 1) < columns && board[i + 1][j + 1] == true)
{
numSurrounding++;
}
if ((i + 1) < rows && (j - 1) >= 0 && board[i + 1][j - 1] == true)
{
numSurrounding++;
}
if ((i - 1) >= 0 && (j + 1) < columns && board[i - 1][j + 1] == true)
{
numSurrounding++;
}
if ((i - 1) >= 0 && (j - 1) >= 0 && board[i - 1][j - 1] == true)
{
numSurrounding++;
}
if (numSurrounding < 2 || numSurrounding > 3)
{
tempBoard[i][j] = false;
}
else if (numSurrounding == 2)
{
tempBoard[i][j] = board[i][j];
}
else if (numSurrounding == 3)
{
tempBoard[i][j] = true;
}
numSurrounding = 0;
}
}
for (int i = 0; i < rows; i++)
{
for (int j = 0; j < columns; j++)
{
board[i][j] = tempBoard[i][j];
}
}
}

Answer 1

You need to use a collection from the STL.
Here's an example that nests vectors to get your board:
#include <vector>
#include <iostream>
using namespace std;
class Board {
int columns, rows;
vector<vector<bool>> board;
public:
Board(int x, int y) : board(vector<vector<bool>>(x, vector<bool>(y))) {
}
void nextFrame() {
// Fill in
}
void printFrame() {
// Fill in
}
size_t xdim() {
return board.size();
}
size_t ydim() {
if (board.size() == 0) {
return 0;
}
return board.at(0).size();
}
};
int main() {
Board b(10, 20);
cout << "Made the board" << endl;
cout << "X: " << b.xdim() << endl;
cout << "Y: " << b.ydim() << endl;
}
You can learn about the member initialization syntax for board(vector<vector<bool>>(x, vector<bool>(y))) here and here.