From: Dave Burt <dave@...>
Date: 2005-06-13T21:20:31+09:00
Subject: Re: Only if the object exists

"Gavin Kistner" <gavin@refinery.com> wrote...
> If I write code like this:
>   self.foo.bar if self.foo
> then ruby runs the #foo method twice. (Javascript is the same way.)
>
> If #foo is a lengthy process which I know has no side-effects, this
> is wasteful. But, I need to ensure that #foo didn't return nil. I
> have (at least) three choices:
>
>   if ( tmp=foo )
>     puts tmp.bar
>   end
>
>   ( tmp=foo ) && ( puts tmp.bar )
>
>   puts tmp.bar if ( tmp=foo )
>
> ..except that the last doesn't work, if 'tmp' has not been
> previously seen as a local variable. Unfortunately, that's the form
> that I really think looks best.

The following method was mentioned a while back, and is a solution to this 
problem.

class NilClass
  def method_missing() nil end
end

Cheers,
Dave