Nokogiri: Finding and XML element then adding child elements

Question

I have an xml document and I want to add child elements under the element with the name 'InitgPty' and I'm attempting to do so as follows:

filename = "#{payment.updated_at.strftime("%Y%m%d")}.xml"
file_contents = File.read("#{filename}")

doc = Nokogiri::XML(file_contents)

initgpty = doc.at_xpath("//InitgPty")
first_id_tag = Nokogiri::XML::Node.new "Id", doc
initgpty.add_next_sibling(first_id_tag)

The problem is that

initgpty = doc.at_xpath("//InitgPty")

returns nil so I'm getting a NoMethodError on .add_next_sibling. This is my first time working with both XML and nokogiri but, to me, the XML generated by

doc = Nokogiri::XML(file_contents)

looks very strange. Here's a snippet from what that line outputs in the rails console:

#<Nokogiri::XML::Element:0x58d9582 name="InitgPty" namespace=#<Nokogiri::XML::Namespace:0x58ce1be href="urn:iso:std:iso:20022:tech:xsd:pain.008.003.02"> children=[#<Nokogiri::XML::Text:0x58d92d0 "\n        ">, #<Nokogiri::XML::Element:0x58d9212 name="Nm" namespace=#<Nokogiri::XML::Namespace:0x58ce1be href="urn:iso:std:iso:20022:tech:xsd:pain.008.003.02"> children=[#<Nokogiri::XML::Text:0x58d8e84 "B8S Chatter Creators">]>, #<Nokogiri::XML::Text:0x58d8d12 "\n      ">]>

Is this correct and the NoMethodError is being caused by something else? Any help at all on this matter would be greatly appreciated.

Answer 1

Try to use CSS selectors. This also works for XML-documents:

doc.css('InitgPty').first
#should return the first element named InitgPty