racer_utils.rb

class Die
  def initialize(sides = 6)
    @sides = sides
  end
  
  # Remember: rand(N) randomly returns one of N consecutive integers, starting at 0
  # So rand(N) returns a random integer in (0..N-1)
  # And 1 + rand(N) returns a random integer in (1..N)
  # See: http://www.ruby-doc.org/core-1.9.3/Kernel.html#method-i-rand
  def roll
    1 + rand(@sides)
  end
end

# Use "reputs" to print over a previously printed line,
# assuming the cursor is positioned appropriately.
def reputs(str = '')
  puts "\e[0K" + str
end

# Clear the screen
def clear_screen!
  print "\e[2J"
end

# Moves cursor to the top left of the terminal
def move_to_home!
  print "\e[H"
end

# Flushes the STDOUT buffer.
# By default STDOUT is only flushed when it encounters a newline (\n) character
def flush!
  $stdout.flush
end

ruby_racer.rb

require_relative 'racer_utils'
 
class RubyRacer
  attr_reader :players, :length
 
  def initialize(players, length = 30)
    @players = players
    @length = length
    @player_positions = {players[0] => 0, players[1] => 0}
  end
  
  # Returns +true+ if one of the players has reached 
  # the finish line, +false+ otherwise
  def finished?
    @player_positions[players[0]] >= length || @player_positions[players[1]] >= length
  end
  
  # Returns the winner if there is one, +nil+ otherwise
  def winner
    return players[0] if @player_positions[players[0]] >= length 
    return players[1] if @player_positions[players[1]] >= length
    return nil   
  end
  
  # Rolls the dice and advances +player+ accordingly
  def advance_player!(player)
    @player_positions[player] += Die.new.roll
  end
  
  # TODO: Print the board. 
  # The board should have the same dimensions each time
  # and you should use the "reputs" helper to print over
  # the previous board
  def print_board
    puts @player_positions
    # reputs "   |" * @player_positions[players[0]] + " #{players[0]} |" + "   |" * (@length - @player_positions[players[0]])
    # reputs "   |" * @player_positions[players[1]] + " #{players[1]} |" + "   |" * (@length - @player_positions[players[1]])
  end
 
end
 
players = ['a', 'b']
 
game = RubyRacer.new(players)
 
# This clears the screen, so the fun can begin
clear_screen!
 
until game.finished?
  players.each do |player|
    # This moves the cursor back to the upper-left of the screen
    move_to_home!
  
    # We print the board first so we see the initial, starting board
    game.print_board
    game.advance_player!(player)
    
    # We need to sleep a little, otherwise the game will blow right past us.
    # See http://www.ruby-doc.org/core-1.9.3/Kernel.html#method-i-sleep
    sleep(0.5)
  end
end
 
# The game is over, so we need to print the "winning" board
game.print_board
 
puts "Player '#{game.winner}' has won!"

ruby_racer_refactored.rb

require_relative 'racer_utils'
 
class RubyRacer
  attr_reader :players, :length
 
  def initialize(players, length = 30)
    @players = players
    @length = length
    @player_positions = Hash.new
    players.each_with_index do |player, index|
      @player_positions[players[index]] = 0
    end
  end

  def finished?
    @player_positions[players[0]] >= length || @player_positions[players[1]] >= length
  end
  
  def winner
    @player_positions.each do |player_symbol, position|
      return player_symbol if position >= @length
    end
  end
  
  def advance_player!(player)
    @player_positions[player] = [ @player_positions[player] + Die.new.roll, @length ].min 
  end
  
  def print_board
    clear_screen!
    move_to_home!
    @player_positions.each do |player_symbol, position|
      reputs " |" * position + "#{player_symbol}|" + " |" * (@length - position)  
    end
  end

  def play
    until self.finished?
      players.each do |player|
        self.print_board
        self.advance_player!(player)
        sleep(0.3)
      end
    end
    self.print_board
    puts "Player '#{self.winner}' has won!"
    puts "BOOYAKASHAAAW!!!" if @players.length > 2
  end

end
 
players = ['a', 'b']
 
game = RubyRacer.new(players)
game.play