From: Josh Cheek <josh.cheek@...>
Date: 2010-10-12T05:19:00+09:00
Subject: Re: more idiomatic way to avoid errors when calling method on variable that may be nil?

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On Mon, Oct 11, 2010 at 3:05 PM, Charles Calvert <cbciv@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?
>
> --
> Charles Calvert
> Moderator - alt.computer.consultants.moderated
> Submission Address: accm@celticwolf.net
> Contact Address: accm_mod@celticwolf.net
>
>
I usually do:
hash = { :key1 => nil , :key2 => "aBcD" }

var = hash[:key1] && hash[:key1].downcase
var # => nil

var = hash[:key2] && hash[:key2].downcase
var # => "abcd"


Notice the nuance that if hash[:key1] is false, that will be assigned to
var.
This also works:

var = hash[:key1].downcase rescue nil
var # => nil

var = hash[:key2].downcase rescue nil
var # => "abcd"


But people seem to really be opposed to doing this. Not entirely sure why.
Maybe because it wouldn't raise an error if, for example, you put some
absurd type of data in your hash?

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