From: Brian Candler <B.Candler@...>
Date: 2003-03-16T08:00:07+09:00
Subject: Re: vcard 0.1 - how to do return values that can have 0, 1, or >1 cardinality

On Sun, Mar 16, 2003 at 07:21:26AM +0900, Sam Roberts wrote:
> I also noticed that Enumrable.find_all() always returns an array, its
> just sometimes it has a size of zero.
> 
> So, I've been drifting towards that.
> 
> Currently, the _all() APIs return an array, or nil, so if the return
> value is true, then there is guaranteed to be at least one member, but
> I'm starting to feel there's a mismatch between this way, and the Ruby
> Way, so I might just always return an array for the _all() functions.
> I'm still thinking about it.
> 
> What to other people do? I don't have experience with enough APIs to
> know.

FWIW, in the DBI library which I have been using quite a lot recently:

  dbh.select_one   returns nil or a row
  dbh.select_all   returns an array of rows, or [] if no rows were found

[] can be convenient because you can do 'each' on the result without having
to test for nil first.

Regards,

Brian.