RSS
reading and writing
Really Simple Syndication (RSS
) is a family of formats that describe ‘feeds,’ specially constructed XML
documents that allow an interested person to subscribe and receive updates from a particular web service. This portion of the standard library provides tooling to read and create these feeds.
The standard library supports RSS
0.91, 1.0, 2.0, and Atom
, a related format. Here are some links to the standards documents for these formats:
Consuming RSS
If you’d like to read someone’s RSS
feed with your Ruby code, you’ve come to the right place. It’s really easy to do this, but we’ll need the help of open-uri:
require 'rss' require 'open-uri' url = 'http://www.ruby-lang.org/en/feeds/news.rss' open(url) do |rss| feed = RSS::Parser.parse(rss) puts "Title: #{feed.channel.title}" feed.items.each do |item| puts "Item: #{item.title}" end end
As you can see, the workhorse is RSS::Parser#parse, which takes the source of the feed and a parameter that performs validation on the feed. We get back an object that has all of the data from our feed, accessible through methods. This example shows getting the title out of the channel element, and looping through the list of items.
Producing RSS
Producing our own RSS
feeds is easy as well. Let’s make a very basic feed:
require "rss" rss = RSS::Maker.make("atom") do |maker| maker.channel.author = "matz" maker.channel.updated = Time.now.to_s maker.channel.about = "http://www.ruby-lang.org/en/feeds/news.rss" maker.channel.title = "Example Feed" maker.items.new_item do |item| item.link = "http://www.ruby-lang.org/en/news/2010/12/25/ruby-1-9-2-p136-is-released/" item.title = "Ruby 1.9.2-p136 is released" item.updated = Time.now.to_s end end puts rss
As you can see, this is a very Builder-like DSL. This code will spit out an Atom
feed with one item. If we needed a second item, we’d make another block with maker.items.new_item and build a second one.
Copyright
Copyright © 2003-2007 Kouhei Sutou <kou@cozmixng.org>
You can redistribute it and/or modify it under the same terms as Ruby.
There is an additional tutorial by the author of RSS
at: www.cozmixng.org/~rwiki/?cmd=view;name=RSS+Parser%3A%3ATutorial.en
The prefix for the Content XML
namespace.
The URI
of the Content specification.
For backward compatibility
The prefix for the Image XML
namespace.
This constant holds strings which contain the names of image elements, with the appropriate prefix.
The prefix for the iTunes XML
namespace.
The URI
of the iTunes specification.
The list of all available libraries for parsing.
The list of all available parsers, in constant form.
For backward compatibility :X
for backward compatibility
The prefix for the Slash XML
namespace.
The prefix for the Taxonomy XML
namespace.
The listing of all the taxonomy elements, with the appropriate namespace.