wrote the Feed.update logic and an initial test spec.

lib/feedzirra/feed.rb

@@ -81,6 +81,37 @@ def self.fetch_and_parse(urls, options = {})
       return responses.size == 1 ? responses.values.first : responses
     end
 
+    def self.update(feeds, options = {})
+      feeds = [*feeds]
+      multi = Curl::Multi.new
+      responses = {}
+      feeds.each do |feed|
+        easy = Curl::Easy.new(feed.feed_url) do |curl|
+          curl.headers["User-Agent"]        = (options[:user_agent] || USER_AGENT)
+          curl.headers["If-Modified-Since"] = feed.last_modified
+          curl.headers["If-None-Match"]     = feed.etag if feed.etag
+          curl.follow_location = true
+          curl.on_success do |c|
+            updated_feed = Feed.parse(c.body_str)
+            updated_feed.feed_url ||= c.last_effective_url
+            updated_feed.etag = etag_from_header(c.header_str)
+            updated_feed.last_modified = last_modified_from_header(c.header_str)
+            feed.update_from_feed(updated_feed)
+            responses[feed.feed_url] = feed
+            options[:on_success].call(feed) if options.has_key?(:on_success)
+          end
+          curl.on_failure do |c|
+            responses[url] = c.response_code
+            options[:on_failure].call(feed, c.response_code, c.header_str, c.body_str) if options.has_key?(:on_failure)
+          end
+        end
+        multi.add(easy)
+      end
+
+      multi.perform
+      return responses.size == 1 ? responses.values.first : responses.values
+    end
+
     def self.etag_from_header(header)
       header =~ /.*ETag:\s(.*)\r/
       $1

lib/feedzirra/feed_utilities.rb

@@ -1,8 +1,12 @@
 module Feedzirra
   module FeedUtilities
-    attr_writer   :last_modified, :new_entries, :updated
+    attr_writer   :new_entries, :updated
     attr_accessor :etag
 
+    def last_modified=(value)
+      @last_modified = value if value
+    end
+
     def last_modified
       @last_modified ||= entries.inject(Time.now - 10.years) {|last_time, entry| entry.published > last_time ? entry.published : last_time}
     end

spec/feedzirra/feed_spec.rb

@@ -176,5 +176,20 @@ def self.able_to_parse?(val)
        #        Feedzirra::Feed.fetch_and_parse(@paul_feed_url).last_modified.should.class == Time
        #      end
     end
+
+    describe "#update" do
+      it "should update and return a single feed object" do
+        feed = Feedzirra::Feed.fetch_and_parse(@paul_feed_url)
+        feed.entries.delete_at(0)
+        feed.last_modified = nil
+        feed.etag = nil
+        updated_feed = Feedzirra::Feed.update(feed)
+        updated_feed.new_entries.size.should == 1
+        updated_feed.should have_new_entries
+      end
+
+      it "should update a collection of feed objects"
+      it "should return the feed objects even when not updated"
+    end
   end
 end