Convert a Nokogiri document to a Ruby Hash

Here's a far simpler version that creates a robust Hash that includes namespace information, both for elements and attributes:

require 'nokogiri'
class Nokogiri::XML::Node
  TYPENAMES = {1=>'element',2=>'attribute',3=>'text',4=>'cdata',8=>'comment'}
  def to_hash
    {kind:TYPENAMES[node_type],name:name}.tap do |h|
      h.merge! nshref:namespace.href, nsprefix:namespace.prefix if namespace
      h.merge! text:text
      h.merge! attr:attribute_nodes.map(&:to_hash) if element?
      h.merge! kids:children.map(&:to_hash) if element?
    end
  end
end
class Nokogiri::XML::Document
  def to_hash; root.to_hash; end
end

Seen in action:

xml = '<r a="b" xmlns:z="foo"><z:a>Hello <b z:m="n" x="y">World</b>!</z:a></r>'
doc = Nokogiri::XML(xml)
p doc.to_hash
#=> {
#=>   :kind=>"element",
#=>   :name=>"r",
#=>   :text=>"Hello World!",
#=>   :attr=>[
#=>     {
#=>       :kind=>"attribute",
#=>       :name=>"a", 
#=>       :text=>"b"
#=>     }
#=>   ], 
#=>   :kids=>[
#=>     {
#=>       :kind=>"element", 
#=>       :name=>"a", 
#=>       :nshref=>"foo", 
#=>       :nsprefix=>"z", 
#=>       :text=>"Hello World!", 
#=>       :attr=>[], 
#=>       :kids=>[
#=>         {
#=>           :kind=>"text", 
#=>           :name=>"text", 
#=>           :text=>"Hello "
#=>         },
#=>         {
#=>           :kind=>"element", 
#=>           :name=>"b", 
#=>           :text=>"World", 
#=>           :attr=>[
#=>             {
#=>               :kind=>"attribute", 
#=>               :name=>"m", 
#=>               :nshref=>"foo", 
#=>               :nsprefix=>"z", 
#=>               :text=>"n"
#=>             },
#=>             {
#=>               :kind=>"attribute", 
#=>               :name=>"x", 
#=>               :text=>"y"
#=>             }
#=>           ], 
#=>           :kids=>[
#=>             {
#=>               :kind=>"text", 
#=>               :name=>"text", 
#=>               :text=>"World"
#=>             }
#=>           ]
#=>         },
#=>         {
#=>           :kind=>"text", 
#=>           :name=>"text", 
#=>           :text=>"!"
#=>         }
#=>       ]
#=>     }
#=>   ]
#=> }

I use this code with libxml-ruby (1.1.3). I have not used nokogiri myself, but I understand that it uses libxml-ruby anyway. I would also encourage you to look at ROXML (http://github.com/Empact/roxml/tree) which maps xml elements to ruby objects; it is built atop libxml.

# USAGE: Hash.from_libxml(YOUR_XML_STRING)
require 'xml/libxml'
# adapted from 
# http://movesonrails.com/articles/2008/02/25/libxml-for-active-resource-2-0

class Hash 
  class << self
        def from_libxml(xml, strict=true) 
          begin
            XML.default_load_external_dtd = false
            XML.default_pedantic_parser = strict
            result = XML::Parser.string(xml).parse 
            return { result.root.name.to_s => xml_node_to_hash(result.root)} 
          rescue Exception => e
            # raise your custom exception here
          end
        end 

        def xml_node_to_hash(node) 
          # If we are at the root of the document, start the hash 
          if node.element? 
           if node.children? 
              result_hash = {} 

              node.each_child do |child| 
                result = xml_node_to_hash(child) 

                if child.name == "text"
                  if !child.next? and !child.prev?
                    return result
                  end
                elsif result_hash[child.name.to_sym]
                    if result_hash[child.name.to_sym].is_a?(Object::Array)
                      result_hash[child.name.to_sym] << result
                    else
                      result_hash[child.name.to_sym] = [result_hash[child.name.to_sym]] << result
                    end
                  else 
                    result_hash[child.name.to_sym] = result
                  end
                end

              return result_hash 
            else 
              return nil 
           end 
           else 
            return node.content.to_s 
          end 
        end          
    end
end