From: "Aníbal" <anibalrojas@...>
Date: 2007-05-30T19:15:15+09:00
Subject: Re: Replacement idiom for "list_or_nil.to_a"?

list_or_nil.each do |value| unless list_or_nil.nil?

--
An�bal Rojas
http://www.rubycorner.com
http://www.hasmanydvelopers.com

On May 25, 6:13 am, Rich Morin <r...@cfcl.com> wrote:
> Many scripting languages, including Ruby, will "do nothing
> gracefully" when asked to iterate through an empty list.
> That is, they iterate NO times.
>
> However, many Ruby methods do not return empty lists when
> nothing is found.  Instead, they return nil.  This means
> that idioms such as:
>
>   list_or_nil.each do |value|
>     ...
>   end
>
> will fail.  As a workaround, I've been using this idiom:
>
>   list_or_nil.to_a.each do |value|
>     ...
>   end
>
> However, I gather that this will soon be deprecated:
>
>  http://www.megasolutions.net/ruby/to_a-68350.aspx
>
> This page suggests putting the list in brackets:
>
>   [list_or_nil]
>
> but this doesn't solve MY problem:
>
>   >> list_or_nil=nil
>   => nil
>   >> [list_or_nil]
>   => [nil]
>
> because the loop will now run once with the value nil.
> I really dislike having to wrap the iteration block in
> an "if" block:
>
>   if list_or_nil
>     list_or_nil.each do |value|
>       ...
>     end
>   end
>
> and this is only marginally better:
>
>   list_or_nil.each do |value|
>     ...
>   end if list_or_nil
>
> I suppose I could define my own to_a method for nil,
> but that seems a bit questionable, as well.  So, is
> there a Better Way To Do It?
>
> -r
> --http://www.cfcl.com/rdm           Rich Morinhttp://www.cfcl.com/rdm/resume    r...@cfcl.comhttp://www.cfcl.com/rdm/weblog    +1 650-873-7841
>
> Technical editing and writing, programming, and web development