How to safely add a class method to your models that affects attributes

application_model.rb

class ApplicationModel < ActiveRecord::Base
  self.abstract_class = true
  
  class_attribute :formatted_attributes_options
  self.formatted_attributes_options = {}
  
  def self.formatted_attributes(*attributes)
    options = attributes.extract_options!
    attributes.each do |attribute|
      formatted_attributes_options[attribute] = options
      
      class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
        remove_method(:#{attribute}) if method_defined?(:#{attribute})
        def #{attribute}(format = nil)
          format_attribute(:#{attribute}, format)
        end
      RUBY_EVAL
    end
  end
  
  def format_attribute(attribute, format = nil)
    value = read_attribute(attribute)
    return value if format.nil?
  
    formatter = formatted_attributes_options[attribute][format]
    raise(ArgumentError.new("#{format} is not a format for #{attribute}")) unless formatter
    
    formatter.respond_to?(:call) ? formatter.call(value) : formatter % value
  end
end

gizmo.rb

class Gizmo < ApplicationModel
  formatted_attributes :price, :short => lamda { |price| ("%.2f" % price).gsub('.00', '.--').gsub('.', ',') }, :nice => ""
end

Thanks, I hope I understand more and more of the call flow later :)