From: Stefano Crocco <stefano.crocco@...>
Date: 2007-03-04T01:07:15+09:00
Subject: Re: YAML issue with Set?

Alle sabato 3 marzo 2007, thebox ha scritto:
> What am I doing wrong?
As far as I can tell (I'm not a YAML expert), no. I've made a few trials, and 
it seems that class Hash (which is used internally by Set), has problems with 
loading / dumping when keys are custom classes. For instance, using irb 
(ruby -v gives ruby 1.8.5 (2006-12-25 patchlevel 12) [i686-linux], on gentoo)
:

>> require 'yaml'
=> true
>> class C
>> end
=> nil
>> c=C.new
=> #<C:0xb78bd5b4>
>> h={c=>'test'}
=> {#<C:0xb78bd5b4>=>"test"}
>> str=YAML.dump h
=> "--- \n!ruby/object:C ? {}\n: test\n\n"
>> h1=YAML.load str
ArgumentError: syntax error on line 2, col -1: `: test

'
        from /usr/lib/ruby/1.8/yaml.rb:133:in `load'
        from /usr/lib/ruby/1.8/yaml.rb:133:in `load'
        from (irb):7
>>

YAML can't convert the string it just produced to a Hash. I've been able (with 
blind trials and using the documentation at 
http://yaml4r.sourceforge.net/cookbook/, in particular the section on ranges) 
to modify the string produced by dump to make it load again. The original 
string is:

---
!ruby/object:C ? {}
: test

The modified one is:

---
? !ruby/object:C {}
: test

It seems that the problem arises from the fact that the dump puts the ? 
(which, if I understand correctly, should mark a hash key) after the type of 
the object (the !ruby/object:C part), while load (correctly, I think) wants 
it before the type.

There is a bug report for this problem: 
http://rubyforge.org/tracker/?group_id=426&atid=1698&func=detail&aid=8886

Stefano