validates_each (ActiveRecord::Validations::ClassMethods)

    # File lib/active_record/validations.rb, line 383
          def validates_each(*attrs)
            options = attrs.extract_options!.symbolize_keys
            attrs   = attrs.flatten

            # Declare the validation.
            send(validation_method(options[:on] || :save)) do |record|
              # Don't validate when there is an :if condition and that condition is false or there is an :unless condition and that condition is true
              unless (options[:if] && !evaluate_condition(options[:if], record)) || (options[:unless] && evaluate_condition(options[:unless], record))
                attrs.each do |attr|
                  value = record.send(attr)
                  next if (value.nil? && options[:allow_nil]) || (value.blank? && options[:allow_blank])
                  yield record, attr, value
                end
              end
            end
          end