如何使用 Nokogiri 和 Ruby 解析 XML 文件

Question

I have a XML file:

<root>
    <person name="brother">Abhijeet</person>
    <person name="sister">pratiksha</person>
</root>

I want it to parse using Nokogiri. I tried by using CSS and XPath but it returns nil or the first element value. How do I retrieve other values? I tried:

doc = Nokogiri::XML(xmlFile)
doc.elements.each do |f|
    f.each do |y|
         p y
    end
end

and:

doc.xpath("//person/sister")
doc.at_xpath("//person/sister")

Answer 1

This is the basic way to search for a node with a given parameter and value using CSS:

require 'nokogiri'

doc = Nokogiri::XML(<<EOT)
<root>
  <person name="brother">Abhijeet</person>
  <person name="sister">pratiksha</person>
</root>
EOT

doc.at('person[name="sister"]').to_html # => "<person name=\"sister\">pratiksha</person>"

You need to research CSS and XPath and how their syntax work. In XPath //person/sister means search everywhere for <sister> nodes inside <person> nodes, matching something like:

<root>
  <person>
    <sister />
  </person>
  <person>
    <sister />
  </person>
</root>

Where it would find all the <sister /> nodes. It doesn't search for the parameter of a node.

Don't do:

doc.elements.each do |f|
    f.each do |y|
         p y
    end
end

You're going to waste a lot of CPU walking through every element. Instead learn how selectors work, so you can take advantage of the power of libXML.