Ruby XML

Ruby allows us to work with XML files with ease. In this tutorial, we will learn how to work with XML files in Ruby.

Syntax

Parsing XML document

To parse an XML document in Ruby we use the REXML library. Here is the syntax for parsing an XML document:

require 'rexml/document'
include REXML

file = File.open("path/to/file.xml")
doc = Document.new file
file.close

Writing XML document

To generate an XML document in Ruby we use the Builder library. Here is the syntax for writing an XML document:

require 'builder'

xml = Builder::XmlMarkup.new(:target => STDOUT)
xml.instruct! :xml, :version => "1.0", :encoding => "UTF-8"
xml.root do
  xml.element1 "value1"
  xml.element2 "value2"
end

Example

Here is an example of how to parse an XML document in Ruby:

require 'rexml/document'
include REXML

file = File.open("books.xml")
doc = Document.new file
file.close

doc.elements.each("catalog/book") do |book|
  puts "Title:       #{book.elements["title"].text}"
  puts "Author:      #{book.elements["author"].text}"
  puts "Description: #{book.elements["description"].text}"
  puts "Price:       #{book.elements["price"].text}"
  puts "------------------------------------------"
end

Output

Title:       Harry Potter
Author:      J.K. Rowling
Description: This is a book about a young boy who discovers he is a wizard.
Price:       19.99
------------------------------------------
Title:       The Lord of the Rings
Author:      J.R.R. Tolkien
Description: This trilogy is an epic adventure story set in the fantasy world of Middle-earth.
Price:       24.99
------------------------------------------

Explanation

In the above example, we are parsing an XML file containing information about books. We open the file using File.open method and pass it to REXML::Document.new constructor which creates an object of REXML::Document class.

We then iterate over all <book> elements using doc.elements.each("catalog/book") method. Within the loop, we use book.elements["element_name"].text to access the value of different elements within the <book> element.

Use

XML is a popular format for data exchange and storage. In Ruby, we can easily parse and generate XML files using the REXML and Builder libraries respectively. XML files are used widely in web services, data exchange between applications, data storage, and many other applications.

Important Points

• Ruby provides built-in support for working with XML files.
• REXML library is used for parsing XML documents.
• Builder library is used for generating XML documents.
• REXML::Document represents an entire XML document.
• REXML::Element represents an XML element.
• doc.elements.each method is used to iterate over elements.
• el.elements["element_name"].text is used to access element's text contents.
• XML is widely used for data exchange and storage.

Summary

In this tutorial, we learned how to work with XML files in Ruby. We discovered that we can easily parse and generate XML files in Ruby using REXML and Builder libraries respectively. We also learned that XML is a popular format for data exchange and storage.