How to get a class to cout as one of its array properties

Question

I'm brand new to C++ (my usual language is Python).

I found out from here how to print an array. I found out from here how to get a class object to cout as one of its properties. And I found out from here that the cout only works if it can access the class's property as a friend.

But, when I combine the answers, it doesn't seem to work. Here's what I've got:

#include <iostream>
using namespace std;

class TicTacToeGame {
    int board[9] = {0, 0, 0, 0, 0, 0, 0, 0, 0};

    friend std::ostream &operator<<(std::ostream &os, TicTacToeGame const &m);
};

std::ostream &operator<<(std::ostream &os, TicTacToeGame const &m) {
    for (int i = 0; i++; i < 9) {
        os << m.board[i];
    }
    return os;
}

int main()
{
    TicTacToeGame game;
    cout << game;
    return 0;
}

And nothing prints on the screen.

What I'd like to see is something along the lines of {0, 0, 0, 0, 0, 0, 0, 0, 0}, but fancy formatting isn't needed as long as I can see the array.

How can I get that to happen?

Standard output is line-buffered by default so any partial line may never appear on your screen; it depends on the OS and calling environment — M.M, May 23 '18 at 02:15
It looks like my answer does that (accidentally) already. Thank you for letting me know that I should keep it like that. — Pro Q, May 23 '18 at 02:16
You need to have at least one more warning enabled: my compile of your code generates: "warning: for increment expression has no effect [-Wunused-value]" — 2785528, May 23 '18 at 03:27
@DOUGLASO.MOEN I'm coding in Atom and using a compiler under the hood so I'm not seeing any of those warnings. Thanks for letting me know. — Pro Q, May 23 '18 at 03:59

score 3 · Accepted Answer · answered May 23 '18 at 02:03

3

Fix the for loop.

for (int i = 0; i++; i < 9) {

should be

for (int i = 0; i < 9; i++) {

answered May 23 '18 at 02:03

user253751

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score 1 · Answer 2 · answered May 23 '18 at 02:10

Thank you to @immibis for reminding me how to do for loops again. (I haven't had to do those in so long...)

Here's the fancier version of the operator function that I decided to go with for the time being, so that it prints out like a tic-tac-toe board.

std::ostream &operator<<(std::ostream &os, TicTacToeGame const &m) {
    for (int i = 0; i < 9; i++) {
        os << m.board[i];
        if (i%3!=2) {
            os << " ";
        }
        if (((i+1) % 3) == 0) {
            os << "\n";
        }
    }
    return os;
}

How to get a class to cout as one of its array properties

2 Answers2