gistfile1.txt

class Card < ActiveRecord::Base
  named_scope :exclude, lambda { |ids|
    { :conditions => ["id NOT IN(?)", ids] }
  }

  # This approach doesn't work when chained to other scopes that limit the number
  # of rows, because count returns a count of all rows.  
  # named_scope :random, lambda { 
  #   { :offset => rand(count), :limit => 1 } 
  # }
  
  # Takes an array with all the cards currently in play,
  # returns a single card from the deck.
  def self.random_from_deck( excludes = [] )
    count = Card.count - excludes.length
    exclude(excludes).find( :first, :offset => rand(count))
  end
end