From: dblack@...
Date: 2006-12-26T23:26:42+09:00
Subject: Re: YAML problem with serializing of nested object structures

Hi --

On Tue, 26 Dec 2006, Kjetil Orbekk wrote:

> Hi!
>
> I'm making a graph tool, and i have some problem with the
> serialization of my graphs. The problem comes when i try to load a
> graph i earlier serialized with YAML. In the objects i serialize, I
> have two instance variables (arrays, as below) that contain some other
> objects of similar type (also serialized). I managed to reproduce the
> problem with a simpler object structure below. To me, this seems very
> wierd, especially since it saves some data and breaks it when
> loading. Could it be a bug, or am I doing something wrong here?
>
> ruby --version is "1.8.4 (2005-12-24) [i486-linux]". My operating
> system is Debian GNU/Linux 4.0.
>
> Ruby code:
> ----------
>
> require "yaml"
>
> # Test class with two instance variables to hold arrays with similar
> # objects
> class Test
>  attr_accessor :c1, :c2
>  def initialize(c1=[], c2=[]) @c1, @c2 = c1, c2 end
> end
>
> a = Test.new
> b = Test.new([a],[Test.new])
> a.c1 << b
> a.c2 << b
>
> # The problem comes when saving the whole thing as an array
> ary = [a, b]
>
> yaml1 = YAML.dump(ary)
>
> # +ary_from_yaml[0]+ looses its c2 even though it's clearly in the YAML output
> ary_from_yaml = YAML.load(yaml1)
>
> yaml2 = YAML.dump(ary_from_yaml)
>
> print "YAML 1\n" + yaml1 + "\n\n"
> print "YAML 2\n" + yaml2 + "\n\n"
>
> print "YAML 1 length: #{yaml1.length} \tYAML 2 length: #{yaml2.length}"

I'm not totally sure but maybe the recursion is causing the problem.
You've got b containing a, and a's attributes containing b.  I'm not
sure how YAML handles that kind of recursion.


David

-- 
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