From: Charles Calvert <cbciv@...>
Date: 2010-10-22T01:55:57+09:00
Subject: Re: more idiomatic way to avoid errors when calling method on variable that may be nil?

On Wed, 20 Oct 2010 22:04:49 -0700 (PDT), w_a_x_man
<w_a_x_man@yahoo.com> wrote in
<42ffdc06-8d05-473b-b271-c5457c67c281@w9g2000prc.googlegroups.com>:

>On Oct 11, 3:02�pm, Charles Calvert <cb...@yahoo.com> wrote:
>> I'm using Ruby 1.8.7 patchlevel 249
>>
>> Is there a more idiomatic way to do the following?
>>
>> var = hash[key].nil? ? nil : hash[key].downcase
>>
>> Note that if hash[key] is nil, I want nil assigned to var, so this
>> won't work:
>>
>> var = hash[key].downcase unless hash[key].nil?
>>
>> Obviously I could do this, but I'm trying to keep it on one line:
>>
>> var = hash[key]
>> var = var.downcase unless var.nil?
>>
>
>var = (t = h[key] and t.upcase) or nil

Using short circuit evaluation to avoid the call to upcase if h[key]
is nil, check.

>var = h[key].tap{|x| x ? x.upcase : nil}

Unfortunately tap is Ruby 1.9, and as I said above, I'm using 1.8.7.

Thanks for the answers.

-- 
Charles Calvert
Moderator - alt.computer.consultants.moderated
Submission Address: accm@celticwolf.net
Contact Address: accm_mod@celticwolf.net