From: Phlip <phlip2005@...>
Date: 2007-09-04T03:28:57+09:00
Subject: Re: Need help in parsing REXML::Document

[Please post raw text; my newsreader chokes on whatever you posted...]

Nikolay Pavlov wrote:

> I have this XML output:

<response>
  <num></num>
  <token></token>
  <operation id="some id" sid="some sid">
    <trans></trans>
    <data></data>
  </operation>
  <operation id="other id" sid="other sid"
    <trans></trans>
    <data></data>
  </operation>
  ...
</response>

> Could someone point me to the way on how i can get construction like this 
> one from the XML above:

{:num => value,
 :token => value,
 :operation => [{:id => value,
                 :sid => value,

I get the idea you want a generic system to turn any stereotypical XML to a 
hash. The XML is too varied to just hard-code the transformation, but the 
XML doesn't contain advanced features like nodes containing both text and 
sub-nodes.

  def git_riddim(node)
    hash = {}
    REXML::XPath.each node, '*' do |node|
      contents = (node.text || '').strip
      (hash[node.name] ||= []) << (contents.blank? ? git_riddim(node) : 
node.text)
    end
    return hash
  end

  def test_recursive_xml_reader
    xml = '<response>
             <num>v1</num>
             <token>v2</token>
             <operation id="some id" sid="some sid">
               <trans>v3</trans>
               <data>v4</data>
             </operation>
             <operation id="other id" sid="other sid">
               <trans></trans>
               <data></data>
             </operation>
           </response>'
    doc = REXML::Document.new(xml)
    hash = git_riddim(doc)
    assert_equal({"response"=>[{"token"=>["v2"], "num"=>["v1"], 
"operation"=>[{"trans"=>["v3"], "data"=>["v4"]}, {"trans"=>[{}], 
"data"=>[{}]}]}]}), hash
  end

Now here's the head-hurting part. We need arrays to turn into objects if 
they only contain one element.

  def reduce_dimensions(hash)
    return unless hash.kind_of?(Hash)
    hash.each do |k,v|
      v.each do |q| reduce_dimensions(q) end
      hash[k] = *v
    end
  end

    reduce_dimensions(hash)

    assert_equal({"response"=>
                  {"token"=>"v2",
                  "num"=>"v1",
     "operation"=>[{"trans"=>"v3", "data"=>"v4"}, {"trans"=>{}, 
"data"=>{}}]}},
                 hash)

We used * to turn arrays of none or one into nil or an object.

Outside of that trick, my code is much more flabby that usual for Hash 
contortions. Someone might be able to use .inject or something to get it 
down to fewer lines, in one pass.

-- 
  Phlip
  http://www.oreilly.com/catalog/9780596510657/
  "Test Driven Ajax (on Rails)"
  assert_xpath, assert_javascript, & assert_ajax