object-oriented.rb

class TicTacToeGame

  def initialize
    @board = Array.new(3) { Array.new(3) }
  end

  def to_s
    board_string = ""

    @board.each do |row|
      row.each do |cell|
        board_string += cell_to_s(cell)
      end
      board_string += "\n"  # print newline to separate rows
    end
    board_string
  end

  def cell_to_s(cell)
    if cell.nil?
      '-'
    else
      cell
    end
  end

  def move(col, row, symbol)
    @board[row][col] = symbol
    puts(self)
  end
end

game = TicTacToeGame.new
game.move(1, 1, 'X')

procedural.rb

board = Array.new(3) { Array.new(3) }

def print_board(board)
  board.each do |row|
    row.each do |cell|
      print_cell(cell)
    end
    puts  # print newline to separate rows
  end
end

def print_cell(cell)
  if cell.nil?
    print '-'
  else
    print cell
  end
end

def move(board, col, row, symbol)
  board[row][col] = symbol
  print_board(board)
end

move(board, 1, 1, 'X')