class FormBuilder < ActionView::Helpers::FormBuilder
    CSS_ERROR_CLASS = 'c1'
    ERRORABLE_FIELDS = [:label, :text_field, :text_area, :check_box, :radio_button]

    ERRORABLE_FIELDS.each do |field|
     class_eval %Q{
        alias :original_#{field} #{field}
        def #{field} (*args, &block)
          if object and object.errors and object.errors.include?(args[0])
            ps = method(:original_#{field}).parameters
            index = ps.index{|a| a[1] == :options }
            args[index] ||= {}
            args[index][:class] ||= ""
            args[index][:class] += " #{CSS_ERROR_CLASS}"
          end
          super(*args, &block)
        end
      }
    end
  end