From: Brian Candler <B.Candler@...>
Date: 2007-03-22T05:18:09+09:00
Subject: Re: nil? with block

On Wed, Mar 21, 2007 at 09:55:07PM +0900, Michiel de Mare wrote:
> If you have a long chain of method calls, but want to check some
> temporary values for nils, for instance to raise an exception,
> currently the easiest way is with local variables:
> 
> e.g.:
> 
> def zipcode_for_user(user)
>   address = user.personal_data.address
>   raise 'no address!' unless address
>   address.zipcode
> end
> 
> If "nil?" is extended to accept a block, and to return self (for
> Object) and the result of the yield (for NilClass), the following
> notation becomes possible:
> 
> user.personal_data.address.nil?{ raise 'no address!'}.zipcode

If your result set doesn't include 'false', then you can use 'or'. Mind you,
it gets ugly with the necessary brackets:

  (user.personal_data.address or raise "no address!").zipcode

Especially if you go to multiple levels. It looks a bit too much like
LISP...

  (((user or raise "no user!").
     personal_data or raise "no personal_data!").
     address or raise "no address!").zipcode

Regards,

Brian.