屏幕报废与nokogiri
我是一个完整的堆栈ruby开发人员。我正在尝试从网站废弃数据，我成功地获取数据。但问题是，下次当我获取数据时，我只想获取新数据我不想覆盖数据库中的所有数据。 我只想添加最近添加的新记录。但我无法找到任何解决方案，如何使用最少的查询和最少的代码。
这是我用于报废的代码：
client = Mechanize.new index_page = client.get('https://www.google.com/') document_page_index = Nokogiri::HTML::Document.parse(index_page.body) page_no_merchant = document_page_index.css('.pagination.pagination-centered ul li:nth-last-child(2) a').text.to_i 1.upto(page_no_merchant) do |page_number| client.get("https://www.google.com/buy-gift-cards?page=#{page_number}") do |page| document = Nokogiri::HTML::Document.parse(page.body) document.css('.product-source').each do |item| merchant_name= item.children.css('.name').text.gsub("Gift Cards", "") puts merchant_name href = item.css('a').first.attr('href') puts href image_url=item.children.css('.img img').attr('data-src').text.strip puts image_url image_url=URI.parse(image_url) @merchant=Merchant.create!(name: merchant_name , image_url:image_url) first_page = client.get("https://www.google.com#{href}") document_page = Nokogiri::HTML::Document.parse(first_page.body) page_no = document_page.css('.pagination.pagination-centered ul li:nth-last-child(2) a').text.to_i 1.upto(page_no) do |page_number_giftcard| type1=[] card_page = client.get("https://www.google.com#{href}?page=#{page_number_giftcard}") document_page = Nokogiri::HTML::Document.parse(card_page.body) document_page.xpath('//table/tbody/tr[@class="toggle-details"]').collect do |row| row.at("td[2] ul").children.each do |typeli| type = typeli.text.strip if typeli.text.strip.length != 0 type1 << type if typeli.text.strip.length != 0 end value = row.at('td[3]').text.strip value = value.to_s.tr('$', '').to_f puts value per_discount = row.at('td[4]').text.strip per_discount = per_discount.to_s.tr('%', '').to_f puts per_discount final_price = row.at('td[5] strong').text.strip final_price = final_price.to_s.tr('$', '').to_f puts final_price puts '******************************' @giftcard=Giftcard.create(card_type:1, card_value:value, per_off:per_discount, card_price: final_price, merchant_id: @merchant.id) end @giftcard.update_attribute() end end end end 先感谢您。
基本上，您通过执行此操作来保存所有数据。
@merchant=Merchant.create!(name: merchant_name , image_url:image_url)
你可以试试像find_or_create_by这样的东西。
@merchant=Merchant.find_or_create_by(name: merchant_name , image_url:image_url)
http://apidock.com/rails/v4.0.2/ActiveRecord/Relation/first_or_create http://apidock.com/rails/v4.0.2/ActiveRecord/Relation/find_or_create_by