From: Ian Macdonald <ian@...>
Date: 2003-08-07T02:26:35+09:00
Subject: Re: What's New and Shiny in Ruby 1.8.0?

On Wed 06 Aug 2003 at 10:17:44 +0900, Harry Ohlsen wrote:

> This would be particularly useful if the data items in the enumeration were 
> instances of more complex objects. Then, you could do things like:
> 
>   sorted = people.sort_by { |p| [p.last_name, p.first_name, p.salary] }

How does one use this with one's own objects, though?

I just cooked up an example Person class to play with and then tried to
sort it as above:

class Person
   include Enumerable

   attr_accessor :first_name, :last_name, :age
 
   def initialize(f,l,a)
     @first_name = f
     @last_name = l
     @age = a.to_i
   end
 end

p [d, g, i, j, p, j2, j3].sort_by { |x| [x.last_name, x.first_name, x.age] }

and I get:

./sort_by:23: undefined method `[]' for #<Person:0x4014e37c>
(NoMethodError)

I'm fine with implementing Person#[], but I can't imagine how it should
look.

Ian
-- 
Ian Macdonald               | If God wanted us to have a President, He
System Administrator        | would have sent us a candidate.   -- Jerry 
ian@caliban.org             | Dreshfield 
http://www.caliban.org      | 
                            |