gistfile1.rb

class Library < Array
  def initialize
    super
  end

  def has_game?(game)
    raise ArgumentError, 'Not a Game object' unless game.is_a?(Game)
    self.select {|i| i == game }.any?
  end

  def games
    self
  end
end

class Game
  attr_accessor :name, :year, :system
  attr_reader   :created_at

  def initialize(name, options={})
    @name   = name
    @year   = options[:year]
    @system = options[:system]

    @created_at = Time.now
  end


  def ==(game)
    raise ArgumentError, 'Not a Game object' unless game.is_a?(Game)

    @name   == game.name   &&
    @system == game.system &&
    @year   == game.year
  end
end

if $0 == __FILE__
  l = Library.new

  game1 = Game.new('Prototype 2', :year => 2012, :system => 'PC')
  game2 = Game.new('Crysis 2', :year => 2012, :system => 'PC')

  l << game1
  p l
  p l.has_game?(game1)
  p l.has_game?(game2)

  l << game2

  p l.has_game?(game2)

  p game1 == game2
  p game1 == game1

  p l.games
end