in tutorials/tutorial3-completed/TicTacToe/TicTacToe/TicTacToeInteractor.swift [60:74]
func placeCurrentPlayerMark(atRow row: Int, col: Int) {
guard board[row][col] == nil else {
return
}
let currentPlayer = getAndFlipCurrentPlayer()
board[row][col] = currentPlayer
presenter.setCell(atRow: row, col: col, withPlayerType: currentPlayer)
if let winner = checkWinner() {
presenter.announce(winner: winner) {
self.listener?.gameDidEnd(withWinner: winner)
}
}
}