From: Brian Lindauer <ruby-lang.org.hop@...>
Date: 2011-07-16T12:43:52+09:00
Subject: [ruby-core:38094] [Ruby 1.9 - Bug #4517] ArgumentError when sorting array of objects


Issue #4517 has been updated by Brian Lindauer.


=begin
I did some investigation into this. The following code does not trigger the error
 class Thing
   attr_accessor :value
 
   def initialize(value)
     @value = value
   end
 end
 
 stuff = [Thing.new("Fred"), Thing.new("Wilma"), Thing.new("Barney")]
 stuff.sort! {|a,b| a.value <=> b.value}
 

Reading through the Ruby source, I discovered that the only way this particular error text could be printed (in (({rb_cmperr()}))) would be if there was a comparison involving a numeric value, not just string/string comparison. Then I tried modifying the input array above to include a numeric value.

  stuff = [Thing.new(4), Thing.new("Wilma"), Thing.new("Barney")]
  stuff.sort! {|a,b| a.value <=> b.value}

This does, in fact, trigger the error.

  in `sort!': comparison of Thing with Thing failed (ArgumentError)

I think the OP must have had a bug in his own code that resulted in a numeric-typed value in one of the instances of Thing.
=end

----------------------------------------
Bug #4517: ArgumentError when sorting array of objects
http://redmine.ruby-lang.org/issues/4517

Author: Milo Thurston
Status: Feedback
Priority: Normal
Assignee: 
Category: 
Target version: 
ruby -v: 1.9.2p180


=begin
I've got some Rails (v. 3.0.4) code wherein an array of objects (referred to as 'Thing' here) need to be sorted:

stuff = array of Things
stuff.sort! {|a,b| a.value <=> b.value }

���where value is a String. 
On Ruby 1.9.2p136 the array "stuff" is sorted successfully, but running the same code on 1.9.2p180 I get the following error:

ArgumentError (comparison of Thing with Thing failed)

I can reproduce the error in the console as well as when running the Rails application.
Thanks for taking a look. 
=end



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