From: Ara.T.Howard@...
Date: 2004-10-12T23:54:36+09:00
Subject: return val of initialize [WAS] Re: tempfiles created by tmpfile removed at exit - can I change this easily?

On Tue, 12 Oct 2004, Robert Klemme wrote:

>>    require 'tempfile'
>>
>>    class Tmpfile < Tempfile
>>      class << self; attr :litter, true; end
>>      def initialize(*a,&b)
>>        t = super
>>        ObjectSpace::undefine_finalizer self if self.class.litter
>>        t
>>      end
>>    end
>
> What do you need that "t" for?  IMHO it's completely superfluous.

i always use a clearly defined return value in my code as, at minimum,
doccumentation.  when i glance at the above it's instantly clear to me (eg.
when re-reading this in six months) that i am doing nothing except removing
the finalizer from the instance and returning it.  in general i find that the
magic ruby rule of returning value of the last statement bad to rely upon in
all but the most simply cases - but for the real reason see below:

> The return value of initialize is always completely ignored.

that cannot be asserted:

   harp:~ > cat a.rb
   class A
     def initialize
       42
     end
     def reinit
       p initialize
     end
   end

   A::new.reinit

   harp:~ > ruby a.rb
   42

if you mean to say that 'the value of initialize is ignored by default for the
single case when it is called by the default Object#new method' then you are
correct.  remember, initialize is simply a method called, in one single case,
to fill in blank objects - it's quite possible and acceptable to call it with
side effects from within the class, or from within subclasses.

in general i think it's poor practice to leave a method with a random return
value: one should return something meaningful and, if that's not possible,
return self to allow chaining.

> Also from an aesthetical point of view, I'd expect the flag "litter" to
> behave exactly the other way round: if litter is true throw it away; you
> keep it if litter is true.

tempfiles are thrown away 'properly' in the normal case - eg. they do not
'litter' /tmp (a very dangerous practice).  i would consider a program that
did not clean up after itself to have 'littered' - but it's of no matter:
change it if you like.

cheers.

-a
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