From: Robert Klemme <bob.news@...>
Date: 2005-05-19T20:30:14+09:00
Subject: Re: RCR 303: nil should accept missing methods and return nil

Klaus Stein wrote:
> John Carter <john.carter@tait.co.nz> wrote:
>> A very simple and generic way of improving the reliability of Ruby
>> programs is to implement the NullObject pattern by allowing nil to
>> accept all and every method instead of throwing a NoMethodError.
>> 
> As far as I understand the whole discussion some wish this behaviour
> to be able to do things like
> 
> obj.meth1().meth2().meth3()
> 
> which should not break if meth2 for some cause returns nil.
> 
> On the other hand many people claim this will hide errors (I agree
> here). It seems there are two kinds of nils: expected and unexpected
> ones. 
> 
> So why dont we deal with the expected ones seperately:
> 
> ==========================================================
> class Object
>   def nil_friendly
>     self
>   end
> end
> 
> class NilClass
>   def nil_friendly
>     Blackhole.instance
>   end
> end
> 
> class Blackhole
>    include Singleton
>    def method_missing( sym, *args)
>      nil
>    end
> end
> 
> ## Now this works:
> 
> obj.meth1().meth2().nil_friendly.meth3()
> ==========================================================
> 
> So by inserting .nil_friendly (choose a better/shorter name for this)
> you _explicitly_ tell that you don't care if nil ist returned.
> 
> This will not break any existing code, will not hide errors, but gives
> shorter code without explicit ifs.
> 
> Comments?

What about #nil?

    robert