gistfile1.rb

require 'rss/2.0'
require 'open-uri'

module ApplicationHelper
  class EmptyURL < RuntimeError
  end

  def rss_content(name)
    content_object = StaticContent.find_by_name(name)
    if content_object.nil? || (Time.now - content_object.updated_at) > 4.hours
      url_object = StaticContent.find_by_name("#{name}_url")
      raise EmptyURL if url_object.nil?
      rss_array = read_rss_feed_into_array(url_object.content)
      # render_content_from_rss_array should be defined in the helper pertaining
      # to whatever controller is calling cached_rss_content
      content = render_content_from_rss_array(rss_array)
      # must update :updated_at because if the content is the same as what is
      # already in the databased, then the database row is not updated, and we
      # would keep checking the URL until the blog contents were changed (ie:
      # caching would only work for the first 4 hours after the blog were updated)
      attributes = { :name => name, :content => content, :updated_at => Time.now }
      if content_object.nil? : StaticContent.create(attributes)
      else content_object.update_attributes(attributes)
      end
    else
      content = content_object.content
    end
    content
  rescue SocketError, EmptyURL, RSS::Error
    if content_object.nil?
      ''
    else
      # something is wrong, update the cache so we don't check every time this
      # is viewed
      content_object.update_attributes(:updated_at => Time.now)
      content_object.content
    end
  end

  private

  def read_rss_feed_into_array(feed_url)
    rss_array = []
    open(feed_url) do |http|
      result = RSS::Parser.parse(http.read, false)
      return [] if result.nil?
      i = 0
      result.items.each do |item|
        rss_array << { :title => item.title,
          :url => item.link,
          :date => item.date,
          :content => item.description }
        i += 1
        break if i > 4
      end
    end
    rss_array
  end
end