From: Eric Mahurin <eric_mahurin@...>
Date: 2005-10-27T23:38:28+09:00
Subject: Re: overriding #inspect

--- Robert Klemme <bob.news@gmx.net> wrote:

> Eric Mahurin wrote:
> > --- Robert Klemme <bob.news@gmx.net> wrote:
> >
> >>>>>> On 10/26/05, Eric Mahurin <eric_mahurin@yahoo.com>
> >> wrote:
> >>>>>>> Anybody know what the best way to override inspect
> where you
> >>>>>>> may have a recursive data structure?
> >
> >
> >> .... which reminds me of an RCR I've been wanting to
> submit
> >> for quite some
> >> time now:
> >> http://rcrchive.net/rcr/show/323
> >>
> >> This could help here, too.
> >>
> >> Kind regards
> >>
> >>     robert
> >
> > Could you describe how this could be used to override
> #inspect?
> >  Or any other example?  I think a ruby implementation RCR
> would
> > go a long way.
> 
> Without going into the details:
> 
> def inspect
>   s = ""
>   traverse(self) do |obj|
>     s << "(" if Enumerable === obj
>     s << do_whatever(obj)
>     s << ")" if Enumerable === obj
>   end
>   s
> end
> 
> It might even be interesting to have a second parameter which
> indicates
> the distance from the start object.  That way indentation
> would be easy
> and maybe it can be used for other stuff as well.  Just an
> idea.

But this wouldn't allow child objects to use their own
#inspect, would it?

I think the best solution for changing the #inspect behavior of
a class would be to have #inspect deal with recursion issues
and call another method (or two) to generate the strings:

def inspect
  # several ways to accomplish this thread-local instance var
  if inspect_thread_local_instance_variable
    inspect_stop
  else
    begin
      inspect_thread_local_instance_variable = true
      inspect_contents
    ensure
      inspect_thread_local_instance_variable = false
  end
end
def inspect_stop
  .. generate an inspect string w/o children ("..." instead) 
end
def inspect_children
  .. generate an inspect string w/ children 
end


With this infrastructure, you could easily change the #inspect
behavior by overriding #inspect_stop and/or #inspect_children. 
No need to worry about recursion.




		
__________________________________ 
Yahoo! FareChase: Search multiple travel sites in one click.
http://farechase.yahoo.com