gistfile1.rb

# this shows how to use the update functionality for a single feed with feedzirra
require 'rubygems'
require 'feedzirra'

# I'm using Atom here, but it could be anything. You don't need to know ahead of time.
# It will parse out to the correct format when it updates.
feed_to_update               = Feedzirra::Parser::Atom.new
feed_to_udpate.feed_url      = some_stored_feed_url
feed_to_update.etag          = some_stored_feed_etag
feed_to_update.last_modified = some_stored_feed_last_modified

last_entry     = Feedzirra::Parser::AtomEntry.new
last_entry.url = the_url_of_the_last_entry_for_a_feed

feed_to_update.entries = [last_entry]

updated_feed = Feedzirra::Feed.update(feed_to_update)

updated_feed.updated?      # => nil if there is nothing new
updated_feed.new_entries   # => [] if nothing new otherwise a collection of feedzirra entries
updated_feed.etag          # => same as before if nothing new. although could change with comments added to entries.
updated_feed.last_modified # => same as before if nothing new. although could change with comments added to entries.