ruby - 如何获取 anchor 标记的 HREF 属性？

Question

我正在尝试从 http://expo.getbootstrap.com/ 中抓取网站

HTML 是这样的:

<div class="col-span-4">
  <p>
    <a class="thumbnail" target="_blank" href="https://www.getsentry.com/">
      <img src="/screenshots/sentry.jpg">
    </a>
  </p>
</div>

我的 Nokogiri 代码是:

url = "http://expo.getbootstrap.com/"
doc = Nokogiri::HTML(open(url))
puts doc.css("title").text
doc.css(".col-span-4").each do |site|
  title=site.css("h4 a").text
  href = site.css("a.thumbnail")[0]['href']
end  

目标很简单，得到 href , <img>标签的 href , 以及网站的 <title> , 但它不断报告:

undefined method [] for nil:NilClass 

行内:

href = site.css("a.thumbnail")[0]['href']

这真的让我发疯，因为我在这里写的代码实际上在另一种情况下工作。

Answer 1

我会做类似的事情:

require 'nokogiri'
require 'open-uri'
require 'pp'

doc = Nokogiri::HTML(open('http://expo.getbootstrap.com/'))

thumbnails = doc.search('a.thumbnail').map{ |thumbnail|
  {
    href: thumbnail['href'],
    src: thumbnail.at('img')['src'],
    title: thumbnail.parent.parent.at('h4 a').text
  }
}

pp thumbnails

其中，运行后有:

# => [
  {
    :href => "https://www.getsentry.com/",
    :src => "/screenshots/sentry.jpg",
    :title => "Sentry"
  },
  {
    :href => "http://laravel.com",
    :src => "/screenshots/laravel.jpg",
    :title => "Laravel"
  },
  {
    :href => "http://gruntjs.com",
    :src => "/screenshots/gruntjs.jpg",
    :title => "Grunt"
  },
  {
    :href => "http://labs.bittorrent.com",
    :src => "/screenshots/bittorrent-labs.jpg",
    :title => "BitTorrent Labs"
  },
  {
    :href => "https://www.easybring.com/en",
    :src => "/screenshots/easybring.jpg",
    :title => "Easybring"
  },
  {
    :href => "http://developers.kippt.com/",
    :src => "/screenshots/kippt-developers.jpg",
    :title => "Kippt Developers"
  },
  {
    :href => "http://www.learndot.com/",
    :src => "/screenshots/learndot.jpg",
    :title => "Learndot"
  },
  {
    :href=>"http://getflywheel.com/",
    :src=>"/screenshots/flywheel.jpg",
    :title=>"Flywheel"
}
]