From: Phlip <phlip2005@...>
Date: 2007-09-08T04:29:25+09:00
Subject: Re: nil.to_s

Nasir Khan wrote:


> IMHO nil.to_s => "", nil.to_i => 0 and nil.to_a => [] are potential 
> sources
> of confusion and bugs.

nil is a potential source of confusion and bugs. Ideally, a method should 
not be called, or it should be called with only relevant data. That's the 
goal of your high-level designing; look up "Null Object Refactor" to learn 
good tips there.

After you allow nils into your equations, you already have the potential 
source of confusion and bugs...

> If anywhere in your code you have statement like
>
> x = y.to_s then you will have to be careful to replace it with
> x = y.nil? ? nil : y.to_s

Google for my illustrious street name, "relevant", and "relevance", all with 
separate sets of quotes (to prevent stemming). My projects use a cute little 
patch on NilObject which takes care of that exact situation:

x = y.relevance

> Is it just me or are there others who have also feel like this?

Ruby's nil handling is exceptionally clean and useful, compared to other 
languages. Some, for example, allow 0 to behave as 'false'. That would be 
bogus in Ruby because 0 is not nil, and nil _does_ behave as false. So we 
allow statements like (x || '') to perform intuitively, without cluttering 
our methods up with excessive 'if' statements.

The price of these conveniences is (x || '') is not as costly as it should 
be. Our programs should have fixed x before they got to this point. But Ruby 
gives the short-term bandaid a lower cost than the long-term cure.

-- 
  Phlip
  http://www.oreilly.com/catalog/9780596510657/
  "Test Driven Ajax (on Rails)"
  assert_xpath, assert_javascript, & assert_ajax