Tic Tac Toe Minimax Algorithm returning empty boards

Question

I've been struggling with implementing a miniMax algorithm for a Tic tac toe AI for a couple of days now. Right now, the problem I'm getting is that I get an empty board in the 'returnBoard' input when I call the minimax() function. I know that my algorithm is going through a series of boards, because I've printed out children as I've got them and I see that the computer is making moves and giving scores to boards. Any suggestions?

void board::getBestMove()
{
board returnBoard;
miniMax(INT_MIN + 1, INT_MAX -1, returnBoard);
*this = returnBoard;
}

int board::miniMax(int alpha, int beta, board & childWithMaximum)
{   
if (checkDone())
    return boardScore();

vector<board> children = getChildren();
for (int i = 0; i < children.size(); ++i)
{
    board curr = children[i];
    //children.pop_back();

    board dummyBoard;
    int score = curr.miniMax(alpha, beta, dummyBoard);

    if (computerTurn)
    {
        if (beta > score)
        {
            beta = score;
            childWithMaximum = curr;    
            if (alpha >= beta) break;
        }
    }

    else 
    {
        if (alpha < score)
        {
            alpha = score;
            childWithMaximum = curr;
            if (alpha >= beta) break;
        }
    }

}
return computerTurn? alpha : beta;
}

vector<board> board::getChildren()
{
vector<board> children;

for (int i = 0; i < 3; ++i)
{   for (int j = 0; j < 3; ++j)
    {
        if (getPosition(i, j) == '*') //move not made here
        {
            board moveMade(*this);
            moveMade.setPosition(i, j);             
            children.push_back(moveMade);
        }
    }
}

return children;
}

Here are the entire runnable contents.

Answer 1

*this = returnedBoard;

This is probably your problem. You should never assign to *this.