From: Matt Armstrong <matt+dated+1010726779.84e909@...>
Date: 2002-01-06T14:26:24+09:00
Subject: [ruby-talk:30332] Re: Ruby article on Freshmeat

HarryO <harryo@zipworld.com.au> writes:

> On Sun, 06 Jan 2002 10:21:32 +1100, Mark Hahn wrote:
>
>
>> Imagine that you want to save text back to a file, but only if it
>> changed:
>> 
>> if str.upcase! then File.open('x.txt','w'){|f| f.write str} end
>
> I can certainly see that's a use for it ... but what's the
> likelihood someone would really want to attempt to change something
> to uppercase and only write it to a file if it changed :-).
>
> Don't worry, I realise you were just giving an example of how the
> feature could be used.  I just don't think it's likely to happen in
> practice, so it doesn't help me understand why the '!' methods are
> designed that way.
>
> I would say that the number of times that happens would be so few,
> compared to the surprise factor having it return nil has, that would
> not be sufficient justification for Matz to have made that design
> decision.
>
> Sounds like Matz could write another book, similar to Bjarne
> Stroustrup's "The Evolution of C++" :-).

I think the official answer is to not use the ! version of the methods
unless you really know what you're doing.  Any given String instance
may be referenced in many different places in a program.  If you
change it with ! as a matter of habit, can run into pretty interesting
bugs.  And usually the performance gain of ! is not necessary.

-- 
matt