From: Eric Hodel <drbrain@...7.net>
Date: 2009-06-06T07:16:56+09:00
Subject: Re: Making nil comparable.

On Jun 5, 2009, at 12:56, Robert Schaaf wrote:

> I have a array of foo objects, each of which contains an array bar  
> values.  I'd like to sort the foos, ordered by the bars.  The  
> problem is that the bars are of unequal length.
>
> The most apt example is the numbering in an outline: 1, 1.1, 1.2,  
> 1.2.1, 1.3 ...etc.
>
> In practical terms, comparing 1.1 to 1.2.1 would be [1, 1, nil] <=>  
> [1, 2, 1].  Array#sort_by barfs on the nil.  Is there some nice way  
> to let nil always sort low?

Don't add nil:

irb(main):003:0> [[1, 1], [1], [1, 1, 2], [2], [1, 2, 1], [1, 3]].sort
=> [[1], [1, 1], [1, 1, 2], [1, 2, 1], [1, 3], [2]]

If you have nil, use #compact on each Array you're sorting first.