From: Robert Klemme <bob.news@...>
Date: 2005-05-06T19:14:25+09:00
Subject: Re: RCR 303: nil should accept missing methods and return nil


"John Carter" <john.carter@tait.co.nz> schrieb im Newsbeitrag 
news:Pine.LNX.4.61.0505061350130.28698@parore.tait.co.nz...
>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.
>
> Not only does this simplify ruby programs considerably, it also
> changes certain crash bugs silently into correct programs.

I'm sorry, is this some kind of hoax?  A program will not magically be 
correct simply because an error is hidden.  Think of all the subtle bugs 
this would introduce, for example: you create an array with a fixed number 
of elements and forget to give the default value 55.  Now math would work, 
but the results would be wrong - and you might not even catch this.

The article at 
http://www.smalltalkchronicles.net/edition2-1/null_object_pattern.htm that 
you refer to in the RCR states, that it's a bad idea to introduce this 
change in Smalltalk because it would break too much code.  The situation in 
Ruby is similar.

> If you were to investigate most cases where an if statement checks to
> see if a value is non-nil, you will find that the else clause is
> empty. ie. Does nothing.

But that would only work in cases like

unless x.nil?
  x.do_something
end

i.e. where the block invokes methods on nil.  This could be safely 
transferred to

x.do_something

with your approach.  But other cases cannot.

Regards

    robert