How do I traverse an inner node using SAX in Nokogiri? - ruby

Question

I'm quite new to Nokogiri and Ruby and seeking a little help.
I am parsing a very large XML file using class MyDoc < Nokogiri::XML::SAX::Document. Now I want to traverse the inner part of a block.
Here's the format of my XML file:
<Content id="83087">
<Title></Title>
<PublisherEntity id="1067">eBooksLib</PublisherEntity>
<Publisher>eBooksLib</Publisher>
......
</Content>
I can already tell if the "Content" tag is found, now I want to know how to traverse inside of it. Here's my shortened code:
class MyDoc < Nokogiri::XML::SAX::Document
#check the start element. set flag for each element
def start_element name, attrs = []
if(name == 'Content')
#get the <Title>
#get the <PublisherEntity>
#get the Publisher
end
end
def cdata_block(string)
characters(string)
end
def characters(str)
puts str
end
end

Answer 1

Purists may disagree with me, but the way I've been doing it is to use Nokogiri to traverse the huge file, and then use XmlSimple to work with a smaller object in the file. Here's a snippet of my code:
require 'nokogiri'
require 'xmlsimple'
def isend(node)
return (node.node_type == Nokogiri::XML::Reader::TYPE_END_ELEMENT)
end
reader = Nokogiri::XML::Reader(File.open('database.xml', 'r'))
# traverse the file looking for tag "content"
reader.each do |node|
next if node.name != 'content' || isend(node)
# if we get here, then we found start of node 'content',
# so read it into an array and work with the array:
content = XmlSimple.xml_in(node.outer_xml())
title = content['title'][0]
# ...etc.
end
This works very well for me. Some may object to mixing SAX and non-SAX (nokogiri and XmlSimple) in the same code, but for my purposes, it gets the job done with minimal hassle.

Answer 2

It's trickier to do with SAX. I think the solution will need to look something like this:
class MyDoc < Nokogiri::XML::SAX::Document
def start_element name, attrs = []
#inside_content = true if name == 'Content'
#current_element = name
end
def end_element name
#inside_content = false if name == 'Content'
#current_element = nil
end
def characters str
puts "#{#current_element} - #{str}" if #inside_content && %w{Title PublisherEntity Publisher}.include?(#current_element)
end
end