ruby 1.8.7 + rails 2.1.0

打开 http://www.google.cn/finance?q=600001 这个网址 可以看到 谷歌财经的 右侧 有个新闻区。。。这个新闻区就是从别的地方抓取来的
截图：


现在我们也来仿照它来实现一个，首先rails解析rss有两种方式，一种是用封装好的类库，一种是用原始的解析xml的方式,或者利用别人封装好的库 例如feedtools, rubyrss 等
用类库的方法：
    require 'rss/2.0'
    require 'open-uri'
    url = "http://news.google.cn/news?pz=1&ned=ccn&hl=zh-CN&topic=b&output=rss"
    @feed = RSS::Parser.parse(open(url).read, false)
    @feed.items.each do |item|
      puts item.title
      puts item.link
      puts  item.description
    end

解析xml的方法：
在lib下建立一个RssParser的类，这样在任何地方都可以调用
class RssParser
  require 'rexml/document'
  def self.run(url)
    xml = REXML::Document.new Net::HTTP.get(URI.parse(url))
    data = {
      :title    => xml.root.elements['channel/title'].text,
      :home_url => xml.root.elements['channel/link'].text,
      :rss_url  => url,
      :items    => []
    }
    xml.elements.each '//item' do |item|
      new_items = {} and item.elements.each do |e|
        new_items[e.name.gsub(/^dc:(\w)/,"\1").to_sym] = e.text
      end
      data[:items] << new_items
    end
    data
  end
end

action中使用：
  def test
    feed = RssParser.run("http://news.google.cn/news?pz=1&ned=ccn&hl=zh-CN&topic=b&output=rss")
    feed1 = feed[:items][0]
    feed2 = feed[:items][0]
    feed3 = feed[:items][0]
    # combine the feeds into an array
    @feeds = [feed1, feed2, feed3]
    # parse the pubDate strings into a DateTime object
    @feeds.each {|x| x[:pubDate] = DateTime.parse(x[:pubDate].to_s)}
    # iterate through each feed, sorting by pubDate
    @feeds.sort! {|a,b| a[:pubDate] <=> b[:pubDate]}
    # reverse the array to sort by descending pubDate
    @feeds.reverse!
    @feeds.each do |feed|
      puts feed[:title]
      puts feed[:link]
      puts feed[:pubDate]
    end
  end

那么上面的title link description 是从哪里来的呢。。。这个是rss2.0的xml结构，一般情况下是这样的：

<?xml version="1.0" encoding="utf-8"?>

<rss version="2.0">

<channel>

         <title>Example Feed</title>

<description>Insert witty or insightful remark here</description>

<link>http://example.org/</link>

<lastBuildDate>Sat, 13 Dec 2003 18:30:02 GMT</lastBuildDate>

<managingEditor>johndoe@example.com (John Doe)</managingEditor>

<item>

<title>Atom-Powered Robots Run Amok</title>

<link>http://example.org/2003/12/13/atom03</link>

<guid isPermaLink="false">urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</guid>

<pubDate>Sat, 13 Dec 2003 18:30:02 GMT</pubDate>

<description>Some text.</description>

</item>

</channel>

</rss>



或者你可以查看rss的页面源代码，或者puts下  @feed = RSS::Parser.parse(open(url).read, false)的结果都可以看到上面的这中xml文档结构



好，下面我们开始实现上面图的新闻：

我们可以把这个部分放在partial里，所以只需要helper和partial文件

helper：

def feed_collection(param)

require 'rss/2.0'

require 'open-uri'

# from news.google.cn

urlhot = "http://news.google.cn/news?pz=1&ned=ccn&hl=zh-CN&topic=b&output=rss"

urlfinance = "http://news.google.cn/news?pz=1&ned=ccn&hl=zh-CN&topic=ecn&output=rss"

urlfund = "http://news.google.cn/news?pz=1&ned=ccn&hl=zh-CN&topic=stc&output=rss"

urlfinancing = "http://news.google.cn/news?pz=1&ned=ccn&hl=zh-CN&topic=pf&output=rss"

case param

when 'hot'

RSS::Parser.parse(open(urlhot).read, false)

when 'finance'

RSS::Parser.parse(open(urlfinance).read, false)

when 'fund'

RSS::Parser.parse(open(urlfund).read, false)

when 'financing'

RSS::Parser.parse(open(urlfinancing).read, false)

end   

end



def feed_link(param)

require 'cgi'

CGI.unescape(param.slice(/(http%).*(&)/)).gsub(/&/,'')  if param # 把十六进制路径 例如http%3A2F之类的转化为 字符

end



def feed_title(param)

param.slice(/.*(-)/).gsub(/-/,"") if param #截取需要的title

end



def feed_from(param)

param.slice(/( - ).*/).from(2) if param # 截取需要的部分

end





partial: _feednews.erb.html

<div class="slides">        

<div><%= render :partial => 'shared/feednews_item',:collection => feed_collection("hot").items %></div>

<div><%= render :partial => 'shared/feednews_item',:collection => feed_collection('finance').items %></div>

<div><%= render :partial => 'shared/feednews_item',:collection => feed_collection('fund').items %></div>

<div><%= render :partial => 'shared/feednews_item',:collection => feed_collection('financing').items %></div>

</div>



主义这里参考了 jquery的loopslider 插件（幻灯片） 加载显示的只是第一个div部分，可以参考：

http://github.com/nathansearles/loopedSlider/tree/master



partial: _feednews_item.html.erb

<ul>

<% unless feednews_item.nil? %>

<li  class="news"><a  href="<%= feed_link(feednews_item.link) %>" target="_blank"><%=  feed_title(feednews_item.title) %></a>



<span class="grey small"><span> <%= feed_from(feednews_item.title) %></span>&nbsp;&mdash;&nbsp;<span><%= feednews_item.pubDate.to_date %></span></span></li>

<% end %>

</ul>

okay....已经成功了，我实现的截图：


ref:
http://www.rubycentral.com/book/ref_c_string.html
http://www.javaeye.com/topic/60620
http://www.troubleshooters.com/codecorn/ruby/basictutorial.htm#_Regular_Expressions
http://paranimage.com/15-jquery-slideshow-plugins/#respond
http://hi.baidu.com/todayz/blog/item/83c1b219d966fd4142a9ad5f.html
http://dennis-zane.javaeye.com/blog/57538
http://sporkmonger.com/projects/feedtools/
http://rubyrss.com/
http://rubyrss.com/
http://www.superwick.com/archives/2007/06/09/rss-feed-parsing-in-ruby-on-rails/
http://www.ruby-forum.com/topic/144447