rbembleton/Chess

Ruby, OOP, AI

Chess

This was started as a project in class with Mac, but expanded Solo to be fully functional, and include a computer AI.

This game features

• OOP
• class inheritance
• error handling
• computer AI
• DRY code

Running Chess

1. First download the zip file here
2. Make sure Ruby is installed by running ruby -v in your console

• If it isn't go to this website for installation instruction

3. Unzip and navigate to the folder using terminal
4. Run bundle install and then ruby chess.rb
5. Have fun! :D

...OK. That all sounds good... but could you walk me through it a bit more?

Sure! Here are some screenshots to help get you started:

bundle install - you should see the gem colorize install

ruby chess.rb - if this doesn't work check your Ruby version with ruby -v and make sure it is 2.0 or higher

Welcome page - enter your name and specify if you'd like to play against the computer AI or a friend

Who needs friends when you have a computer to play Chess against?!

Follow the on screen controls to navigate, and enjoy! (For optimal game play zoom in using ⌘+)

Implementation

To check for valid moves Chess uses to move methods: one which will move regardless of whether the move is valid or not, and the other which will check that the move is valid before proceeding.

## board.rb

def move!(start_pos, end_pos) # Doesn't check for valid move, or update pieces' positions
  @previous_move = [start_pos, end_pos]
  @temp_rm_piece = self[end_pos]
  self[start_pos], self[end_pos] = nil, self[start_pos]
end

def move(start_pos, end_pos)
  begin
    valid_move?(start_pos, end_pos)
  rescue StartingPosition => e
    retry
  end
  move!(start_pos, end_pos)
  self[end_pos].position = end_pos
  @temp_rm_piece.position = nil if @temp_rm_piece.is_a?(Piece)
end

This is necessary because valid_move calls the piece::valid_moves which then calls move! to check whether a move is valid or not, and so this prevents it from calling itself and entering into an infinite loop.

## board.rb

def valid_move?(start_pos, end_pos)
  self[start_pos].valid_moves.include?(end_pos)
end

## piece.rb

def valid_moves # King has his own
  temp_valid_moves = []
  possible_moves.each do |move|
    @board.move!(self.position, move)
    temp_valid_moves << move unless @board.in_check?(self.color)
    @board.undo_last_move
  end
  temp_valid_moves
end