Bug #4517: ArgumentError when sorting array of objects

• Status: Third Party's Issue
• Assignee: -
• Target version: -
• ruby -v: 1.9.2p180

[knirirr (Milo Thurston)]

=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

[ko1 (Koichi Sasada)]

Could you show the reproducible code?

[naruse (Yui NARUSE)]

• Status changed from Open to Feedback

[jbl26 (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

[nagachika (Tomoyuki Chikanaga)]

• Status changed from Feedback to Third Party's Issue