From: why the lucky stiff <ruby-talk@...>
Date: 2003-08-29T01:51:14+09:00
Subject: Re: YAMLand rbtree, was: Re: sorting on hash contents

On Thursday 28 August 2003 02:27 am, Joel VanderWerf wrote:
> I notice that rbtree works with Marshal, but not YAML. What methods
> would have to be added to rbtree to fix this?

Currently, RBTree would need to inherit from Hash (or) introduce custom 
is_complex_yaml?, to_yaml_type and to_yaml methods.

Here's custom methods which appear to work:

  # Emitting the class
  class RBTree
      def to_yaml_type
          "!ruby/rbtree"
      end 
      def to_yaml( opts = {} ) 
          YAML::quick_emit( self.object_id, opts ) { |out|
              out.map( to_yaml_type ) { |map|
                  map.concat( self.to_a )
              }   
          }   
      end 
  end 

  # Loading the class
  YAML.add_ruby_type( 'rbtree' ) { |type, val|
      r = RBTree.new
      val.each { |k, v| r[k] = v }
      r
  }   

  # Test
  a = RBTree['ducks', 100, 'bears', 12, 'badgers', 0]
  puts a.to_yaml
  p YAML::load( a.to_yaml )

  # Looks like...
  --- !ruby/rbtree 
  badgers: 0
  bears: 12
  ducks: 100

I'm not very happy with this technique though.  I'd rather it was simpler, 
such as:

  class RBTree
    include YamlHashMixin
  end

_why