Delete an element after the element is found in Ruby using libxml

I come from C background but working on some stuff related to XML in Ruby, so, please bear with me if my question is naive.

I have one XML document. I am parsing it using libxml:

<test>
 <ready>
  <ex_success>true</ex_success>
 </ready>
 <ath>
  <name>abc</name>
  <pass>123</pass>
  <ex_success>true</ex_success>
 </ath>
</test>

In this document, I am able to read the ex_success element. However, I am not able to delete it from my original file.

Here is my little piece of code:

require 'xml'
test_file = @file_name
parser = XML::Parser.file(test_file)
document = parser.parse

document.root.each_element {|element|

  # Write each element name in the file
  puts 'element.name'

  if val = element.find_first('ex_success')   
    puts val.content   # prints true
    val.remove!    # THIS line does not remove the element from my original file

  else
    puts 'Not found'
  end

What am I doing wrong and what is the right way to delete it?

Solution

I'd recommend not using libxml. While it's part of Ruby, it's not the defacto standard for XML parsing for Ruby. Nokogiri is.

Here's how I'd do it using Nokogiri:

require 'nokogiri'

doc = Nokogiri::XML::DocumentFragment.parse(<<EOT)
<test>
 <ready>
  <ex_success>true</ex_success>
 </ready>
 <ath>
  <name>abc</name>
  <pass>123</pass>
  <ex_success>true</ex_success>
 </ath>
</test>
EOT

ex_success = doc.at('ex_success')
ex_success_value = ex_success.text # !> assigned but unused variable - ex_success_value
ex_success.remove

puts doc.to_xml
# >> <test>
# >>  <ready>
# >>   
# >>  </ready>
# >>  <ath>
# >>   <name>abc</name>
# >>   <pass>123</pass>
# >>   <ex_success>true</ex_success>
# >>  </ath>
# >> </test>

If you don't want the blank line left by the empty text node, use this:

ex_success = doc.at('ex_success')
ex_success_value = ex_success.text # => "true"
ex_success.parent.children.remove

puts doc.to_xml
# >> <test>
# >>  <ready/>
# >>  <ath>
# >>   <name>abc</name>
# >>   <pass>123</pass>
# >>   <ex_success>true</ex_success>
# >>  </ath>
# >> </test>

I used Nokogiri::XML::DocumentFragment.parse, which accepts an XML snippet as-is. It's more common to use Nokogiri::XML(<<EOT), which will add the XML decl if it's not there.