Convenience methods for storing price-like columns as cents, to avoid floating point math!

stored_as_cents.rb

module StoredAsCents
  def stored_as_cents(*methods)
    methods.each do |m|
      define_method "#{m}=" do |value|
        cents = (value.to_f * 100).round
        write_attribute "#{m}_in_cents", cents
      end
      
      define_method m do
        cents = read_attribute "#{m}_in_cents"
        float_value = cents.to_i / 100.0
        int_value = float_value.to_i
        float_value == int_value ? int_value : float_value
      end
      
      define_method "#{m}_changed?" do
        send "#{m}_in_cents_changed?"
      end
      
      define_method "#{m}?" do
        send "#{m}_in_cents?"
      end
    end
  end
end

ActiveRecord::Base.extend StoredAsCents