From: Benoit Daloze <eregontp@...>
Date: 2010-10-22T04:23:10+09:00
Subject: Re: more idiomatic way to avoid errors when calling method on variable that may be nil?

On 21 October 2010 07:05, w_a_x_man <w_a_x_man@yahoo.com> wrote:
> 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

h[key] will return nil if key is not found, so you do not need that "or nil"

  var = (t = h[key] and t.upcase)

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

That is not gonna work, Object#tap return receiver.
So the only way to modify the object "tapped" is to call mutating methods on it:

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