From: Ross Bamford <rossrt@...>
Date: 2006-03-05T02:06:10+09:00
Subject: Re: Kirbybase Hacks NilClass

On Sun, 2006-03-05 at 01:37 +0900, James Edward Gray II wrote:
> I'm examining Kirbybase for use it a project and was surprised to  
> find this bit of code in it:
> 
> #----------------------------------------------------------------------- 
> ----
> # NilClass
> #----------------------------------------------------------------------- 
> ----
> class NilClass
>       
> #-----------------------------------------------------------------------
>      # method_missing
>       
> #-----------------------------------------------------------------------
>      #
>      # This code is necessary because if, inside a select condition code
>      # block, there is a case where you are trying to do an expression
>      # against a table field that is equal to nil, I don't want a method
>      # missing exception to occur.  I just want the expression to be  
> nil.  I
>      # initially had this method returning false, but then I had an  
> issue
>      # where I had a YAML field that was supposed to hold an Array.   
> If the
>      # field was empty (i.e. nil) it was actually returning false  
> when it
>      # should be returning nil.  Since nil evaluates to false, it  
> works if I
>      # return nil.
>      # Here's an example:
>      # #select { |r| r.speed > 300 }
>      # What happens if speed is nil (basically NULL in DBMS terms)?   
> Without
>      # this code, an exception is going to be raised, which is not  
> what we
>      # really want.  We really want this expression to return nil.
>      def method_missing(method_id, *stuff)
>          return nil
>      end
> end
> 
> This has been a popular discussion lately, but I just don't think  
> loading a database library should fundamentally change the language.   
> ActiveRecord doesn't hack NilClass and we seem to do okay with that.   
> Why can't the above example just be coded as:
> 
>    select { |r| r.speed and r.speed > 300 }
> 
> or:
> 
>    select { |r| r.speed > 300 rescue false }
> 
> Are Kirbybase users really liking this behavior?
> 
> James Edward Gray II

I've never used KirbyBase, but from this it looks like it could just
catch NoMethodError in #select...? Introducing this new behaviour to nil
could seriously suck in at least one case I can think of: while coding
stuff up I often get a nomethoderror for nil telling me I'm off by one
or have passed silly arguments...

-- 
Ross Bamford - rosco@roscopeco.REMOVE.co.uk