From: "David A. Black" <dblack@...>
Date: 2010-10-12T06:33:22+09:00
Subject: Re: more idiomatic way to avoid errors when calling method on variable that may be nil?

Hi --

On Tue, 12 Oct 2010, Charles Calvert 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?

It actually will work if var has not been initialized before. But that's
more or less an artifact of how the parser treats local variable
assignment expressions, and is pretty fragile:

   >> hash = {}
   => {}
   >> var = hash[1].downcase unless hash[1].nil?
   => nil
   >> var
   => nil
   >> var2 = "something"
   => "something"
   >> var2 = hash[1].downcase unless hash[1].nil?
   => nil
   >> var2
   => "something"


David

-- 
David A. Black, Senior Developer, Cyrus Innovation Inc.

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