紅寶石，使用Nokogiri和媒體：縮略圖

Question

我已經無休止地搜索這個解決方案，我想我已經解決了它，當我有一個圖像顯示。但是縮略圖只是存儲在根元素中的縮略圖。很簡單這個工程：

rss = Nokogiri::XML(open('http://newsrss.bbc.co.uk/rss/newsonline_uk_edition/front_page/rss.xml')) 
@news = rss.xpath('//item').map do |i| 
    { 
    'title'  => i.xpath('title').text, 
    'link'  => i.xpath('link').text, 
    'description' => i.xpath('description').text, 
    'thumbnail' => i.xpath('//media:thumbnail').attr('url') 
    } 
end 

但編輯媒體：縮略圖來引用該項目似乎打破它：

{ 
    'title'  => i.xpath('title').text, 
    'link'  => i.xpath('link').text, 
    'description' => i.xpath('description').text, 
    'thumbnail' => i.xpath('media:thumbnail').attr('url') 
} 

我不明白，爲什麼作爲兩個元素是相同的。任何指針正確的方向將不勝感激。

謝謝！

Answer 1

您的代碼在沒有縮略圖子元素的第一個元素中斷。試試這個：

@news = rss.xpath('//item').map do |i| 
    thumb = i.at_xpath('media:thumbnail').attr('url') if i.at_xpath('media:thumbnail') 
    { 
    'title' => i.at_xpath('title').text, 
    'link' => i.at_xpath('link').text, 
    'description' => i.at_xpath('description').text, 
    'thumbnail' => thumb 
    } 
end 

現在thumbnail要麼是URL，如果它存在或nil，如果它沒有。

Answer 2

只是爲了比較，這裏的訪問使用引入nokogiri節點的一些其他方法：

require 'ap' 
require 'open-uri' 
require 'nokogiri' 

rss = Nokogiri::XML(open('http://newsrss.bbc.co.uk/rss/newsonline_uk_edition/front_page/rss.xml')) 

# check for parsing errors... 
puts "Errors exist" if (rss.errors.any?) 

# use CSS accessors for simplicity... 
news = rss.search('item').map { |i| 

    # use CSS's namespace wildcard... 
    thumbnail = i.at('media|thumbnail') 
    begin 
    url = thumbnail['url'] 
    rescue 
    url = '' 
    end 
    { 
    'title'  => i.search('title').text, 
    'link'  => i.search('link').text, 
    'description' => i.search('description').text, 
    'thumbnail' => url 
    } 
} 

ap [*news[0 .. 1], *news[-2 .. -1]] 
# >> [ 
# >>  [0] { 
# >>    "title" => "Royal attack 'not down to radios'", 
# >>    "link" => "http://www.bbc.co.uk/go/rss/int/news/-/news/uk-11975280", 
# >>   "description" => "Police deny that a car carrying the Prince of Wales was caught up in student protests because of a breakdown in radio communications.", 
# >>   "thumbnail" => "http://news.bbcimg.co.uk/media/images/50372000/jpg/_50372715_010819577-1.jpg" 
# >>  }, 
# >>  [1] { 
# >>    "title" => "Pope Anglican offer 'dented ties'", 
# >>    "link" => "http://www.bbc.co.uk/go/rss/int/news/-/news/uk-11974543", 
# >>   "description" => "Britain's ambassador to the Vatican feared a backlash over the Pope's invitation to Anglicans to switch churches, according to leaked US cables.", 
# >>   "thumbnail" => "http://news.bbcimg.co.uk/media/images/48697000/jpg/_48697938_007958675-1.jpg" 
# >>  }, 
# >>  [2] { 
# >>    "title" => "Playing defence", 
# >>    "link" => "http://news.bbc.co.uk/go/rss/int/news/-/1/hi/programmes/from_our_own_correspondent/9275324.stm", 
# >>   "description" => "The friendly face of township where honeymoon bride was killed", 
# >>   "thumbnail" => "http://news.bbcimg.co.uk/media/images/50385000/jpg/_50385343_football_afp.jpg" 
# >>  }, 
# >>  [3] { 
# >>    "title" => "Newspaper review", 
# >>    "link" => "http://www.bbc.co.uk/go/rss/int/news/-/news/uk-11975338", 
# >>   "description" => "Papers reflect on attack on royal car", 
# >>   "thumbnail" => "http://news.bbcimg.co.uk/media/images/49254000/jpg/_49254932_efb006dc-dd09-47bd-8f2d-37752152f772.jpg" 
# >>  } 
# >> ] 

注意使用CSS命名空間通配符。如果您不關心文檔中的命名空間並想要處理所有內容，它可以使您的生活變得更加輕鬆。