Ruby XML, XSLT And XPath Tutorial

Let's go over how you can work with XML, XSLT, and XPath in Ruby.

Ruby provides several libraries to work with XML. In this tutorial, we'll use Nokogiri, a popular gem that can read, write, and manipulate XML (and HTML) documents. It also provides support for XSLT transformations and XPath queries.

1. Installing Nokogiri

Before you start, you need to install the Nokogiri gem. You can do this by running:

gem install nokogiri

2. Parsing XML

You can create an XML document from a string or a file:

require 'nokogiri'

# From a string
xml_string = '<root><child>Hello, world!</child></root>'
doc = Nokogiri::XML(xml_string)

# From a file
doc = Nokogiri::XML(File.open('document.xml'))

3. Querying XML with XPath

Once you have a Nokogiri::XML::Document, you can use XPath to query the XML:

nodes = doc.xpath('//child')
nodes.each do |node|
  puts node.text  # Outputs: Hello, world!
end

4. Modifying XML

You can also modify XML documents:

node = doc.at_xpath('//child')
node.content = 'Goodbye, world!'
puts doc.to_xml  # Outputs: <?xml version="1.0"?>\n<root>\n  <child>Goodbye, world!</child>\n</root>\n

5. Applying XSLT Stylesheets

Nokogiri supports XSLT transformations:

xslt_string = <<-XSLT
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:template match="/root">
    <newRoot>
      <newChild><xsl:value-of select="child"/></newChild>
    </newRoot>
  </xsl:template>
</xsl:stylesheet>
XSLT

xslt = Nokogiri::XSLT(xslt_string)

new_doc = xslt.transform(doc)
puts new_doc.to_xml  # Outputs: <?xml version="1.0"?>\n<newRoot>\n  <newChild>Goodbye, world!</newChild>\n</newRoot>\n

This is a basic introduction to working with XML, XSLT, and XPath in Ruby using Nokogiri. Depending on your use case, you might need to handle namespaces, errors, more complex XPath queries, or other XML features. Be sure to check the Nokogiri documentation for more details.

Parsing XML with Ruby: Use the built-in REXML library for XML parsing.

require 'rexml/document'

xml_string = '<root><element>Value</element></root>'
xml_document = REXML::Document.new(xml_string)

Creating XML documents in Ruby: Build XML documents programmatically with REXML.

require 'rexml/document'

xml_document = REXML::Document.new
root = xml_document.add_element('root')
element = root.add_element('element')
element.text = 'Value'

Ruby XML namespaces: Work with XML namespaces using REXML.

require 'rexml/document'

xml_document = REXML::Document.new
root = xml_document.add_element('root', 'xmlns:prefix' => 'http://example.com')

Transforming XML with XSLT in Ruby: Apply XSLT transformations using LibXSLT.

require 'libxslt'

xslt = LibXSLT::XSLT.parse(File.read('transform.xslt'))
result = xslt.apply(xml_document)

Applying XSLT stylesheets in Ruby: Apply XSLT stylesheets using REXML.

require 'rexml/document'
require 'rexml/xslt'

xml_document = REXML::Document.new(xml_string)
xslt_stylesheet = REXML::Document.new(File.read('transform.xslt'))
result = REXML::XSLT.new(xslt_stylesheet).apply(xml_document)

Using XPath with Ruby: Navigate XML documents using XPath.

require 'rexml/document'

xml_document = REXML::Document.new(xml_string)
element_value = REXML::XPath.first(xml_document, '//element').text

Ruby XPath examples: Perform XPath queries with REXML.

require 'rexml/document'

xml_document = REXML::Document.new(xml_string)
elements = REXML::XPath.match(xml_document, '//element')

Searching and querying XML in Ruby: Use various methods to search and query XML documents.

require 'nokogiri'

xml_document = Nokogiri::XML(xml_string)
element_value = xml_document.at('//element').text

Ruby XML validation: Validate XML against a schema or DTD using Nokogiri.

require 'nokogiri'

xml_document = Nokogiri::XML(xml_string)
schema = Nokogiri::XML::RelaxNG(File.read('schema.rng'))
validation_result = schema.valid?(xml_document)

Ruby XML libraries comparison: Compare XML libraries like REXML, LibXML, and Nokogiri.
```
# Choose the appropriate library based on your requirements
```
Processing XML with Nokogiri in Ruby: Utilize the powerful Nokogiri library for XML processing.
```
require 'nokogiri'

xml_document = Nokogiri::XML(xml_string)
```
Working with RSS or Atom feeds in Ruby: Parse and manipulate RSS or Atom feeds using relevant libraries.
```
require 'rss'

rss_feed = RSS::Parser.parse(rss_xml)
```