From: Robert Klemme <shortcutter@...>
Date: 2010-10-13T18:18:45+09:00
Subject: Re: more idiomatic way to avoid errors when calling method on variable that may be nil?

On Wed, Oct 13, 2010 at 7:45 AM, Tony Arcieri <tony.arcieri@medioh.com> wrote:
> On Tue, Oct 12, 2010 at 6:39 AM, Rick DeNatale <rick.denatale@gmail.com>wrote:
>
>> Nobody seems to have mentioned it, I guess since this is the place for
>> 'pure' rubyists, but Rails has the following methods:
>>
>> So with this you can write simply
>>
>>   var =  hash[key].try(:downcase)
>>
>
> That's pretty cool, but I'd prefer it return a proxy object for all non-nil
> objects that just relays the method call, and for nil a proxy that always
> returns nil, ala:
>
> hash[key].try.downcase

Like this?

require 'singleton'

class NilProxy
  include Singleton
  def method_missing(*a,&b) end
end

class Object
  def try
    self
  end
end

class NilClass
  def try
    NilProxy.instance
  end
end

["Foo", nil, "Bar"].each do |x|
  p x.try.downcase
end

Kind regards

robert


-- 
remember.guy do |as, often| as.you_can - without end
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