Format attributes when they are set in ActiveRecord

format_attributes.rb

module FormatAttribute
  unloadable
  
  def self.included(base)
    base.class_eval do
      class << self
        # format :cash, :except => "$"
        # format :date do |value|
        #   Date.parse(value)
        # end
        def format(attr_name, options = {}, &block)
          formats[attr_name.to_sym] = [options, block]
        end

        def formats
          @formats ||= {}
        end
      end
      
      def write_attribute_with_formatting(attr_name, value)
        write_attribute_without_formatting(attr_name, formatted_value(attr_name, value))
      end
      
      def formatted_value(attr_name, value)
        format = self.class.formats[attr_name.to_sym]
        if format.present? && value.present?
          options = format[0]
          block   = format[1]
          value   = value.to_s.gsub(options[:except], "") if options[:except].present?
          value   = block.call(value)                     if block.present?
          value   = self.class.columns_hash[attr_name.to_s].type_cast(value)          
          value
        else
          value
        end
      end
      
      alias_method_chain :write_attribute, :formatting
    end
  end
end

ActiveRecord::Base.send(:include, FormatAttribute)