From: Joel VanderWerf <vjoel@...>
Date: 2006-09-19T04:19:10+09:00
Subject: Re: YAML bug: custom key types in a Hash

reddaly@gmail.com wrote:
> I believe this is a YAML bug, or at least a place that needs a more
> useful error message.  When I define a Hash with a custom key type,
> YAML has trouble.  The following code should demonstrate the problem:
> 
> class X;
>   def initialize(foo)
>     @foo = foo;
>   end;
> end;
> 
> YAML::load({X.new("bar") => "sailor" }.to_yaml)
> # =>
> ArgumentError: syntax error on line 2, col -1: `  foo: bar
> : sailor
> 
> '
>         from /usr/lib/ruby/1.8/yaml.rb:133:in `load'
>         from /usr/lib/ruby/1.8/yaml.rb:133:in `load'
>         from (irb):15
>         from :0
> 
> I'd appreciate any help in getting this to work. If this is truly a
> bug, perhaps somebody can tell me how to report it.

As a quick workaround, maybe the following will help. It forces yaml to 
use a reference instead of the X object itself. A reference seems to be 
more easily parsed as a hash key.

require 'yaml'

class X
   def initialize(foo)
     @foo = foo
   end
end

x = X.new("bar")
h = {x => "sailor"}

puts [x,h].to_yaml

ary = YAML::load([x,h].to_yaml)

puts
p ary[1]


and the output is:

---
- &id001 !ruby/object:X
   foo: bar
- *id001: sailor

{#<X:0xb7b7be6c @foo="bar">=>"sailor"}


-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407