From: Mike Wyer <mike@...>
Date: 2003-02-08T02:19:45+09:00
Subject: Re: Ruby "Procedures" & their return values

On Sat, 8 Feb 2003, Austin Ziegler wrote:

> [Please note that I am way behind on my ruby-talk reading. If you need a quick response, email me directly.]
>
> In the thread on return values from assertions, I have seen a couple of
> people express that they prefer functions/methods without meaningful
> return values to return nil. Given that Ruby is a dynamically typed,
> expression-oriented language, this makes no sense to me.
>
> Even if the return value of a method is meaningless and not guaranteed
> to be something useful (a documentation matter, IMO), that doesn't mean
> that it doesn't provide value. In particular, since nil is a Boolean
> false value, returning nil from these methods means that the method
> cannot be used in a test, as it is always "false".
>

If the method fails, it should raise an exception. In which case the
return value is worthless- if it would be false, you'd never know because
the exception would already have been triggered.

Testing a meaningless output should be discouraged by always having the
method return nil. It's painful for C developers to trust the exception
mechanism, but it makes for much cleaner code.

begin
  do_thing
  do_other_thing
  foo
rescue BadThing
  warn_bad_thing
end

versus

begin
  if do_thing
    if do_other_thing
      foo
    else
      warn_bad_thing
    endif
  else
    warn_bad_thing
  endif
end

Sure, there are ways of cleaning up this construction, but the principle
remains. Don't encourage bad habits by ignoring them or even supporting
them. Return nil and you can help people do the right thing.

Cheers,
Mike
-- 
Mike Wyer     <mike@wyer.org>     www.wyer.org/mike     07974 254007

    "I want to die peacefully in my sleep like my Grandfather...
  ... not screaming and yelling like the passengers in his car"