From: "Chr. Rippel" <chr_news@...>
Date: 2002-01-28T00:34:14+09:00
Subject: Re: Subrange of String subclass => invalid object

"Tobias Reif" <tobiasreif@pinkjuice.com> wrote in,
....
There are two ways of resolving this inconsistency - I would prefer if
these operation would always return a String since this is an accordance
with the general behavior - i.e. if you want #upcase return a Foo it should
be your responsiblity to override it (a simple #dup.upcase!)

Thinking about it - if the implementation of #upcase is changed to
----
class String
    def upcase
         dup.upcase!
    end
end

# then the subclassing behavior becomes logical and works
# as expected

class HistoryString  < String
 def initialize (str)
    super
    @orig_length = length
 end
 def dup
    (res = super).orig_length = length
     res
 end
 alias clone dup
 attr_accessor :orig_length
end


qwert2 = (HistoryString.new 'qwert').concat  'qwert'
qwert2.concat p qwert2.orig_length   # => 5
p qwert2.upcase.orig_length              # => 10
----
I guess this would be fine with me - in general I am not a fan
of type-magic.


/Christoph