changes_from_nil_to_empty_string?

# File activerecord/lib/active_record/attribute_methods/dirty.rb, line 97
      def changes_from_nil_to_empty_string?(column, old, value)
        # For nullable numeric columns, NULL gets stored in database for blank (i.e. '') values.
        # Hence we don't record it as a change if the value changes from nil to ''.
        # If an old value of 0 is set to '' we want this to get changed to nil as otherwise it'll
        # be typecast back to 0 (''.to_i => 0)
        column.null && (old.nil? || old == 0) && value.blank?
      end