如何使用Rails緩存來存儲Nokogiri對象？

Question

我正在使用Rails 5來使用Rails緩存來存儲Nokogiri對象。

我在配置/初始化/ cache.rb創造了這個：

$cache = ActiveSupport::Cache::MemoryStore.new 

，我想保存文件一樣：

$cache.fetch(url) { 
    result = get_content(url, headers, follow_redirects) 
} 

，但我得到這個錯誤：

Error during processing: (TypeError) no _dump_data is defined for class Nokogiri::HTML::Document 
/Users/davea/.rvm/gems/ruby-2.4.0/gems/activesupport-5.0.2/lib/active_support/cache.rb:671:in `dump' 
/Users/davea/.rvm/gems/ruby-2.4.0/gems/activesupport-5.0.2/lib/active_support/cache.rb:671:in `dup_value!' 
/Users/davea/.rvm/gems/ruby-2.4.0/gems/activesupport-5.0.2/lib/active_support/cache/memory_store.rb:128:in `write_entry' 
/Users/davea/.rvm/gems/ruby-2.4.0/gems/activesupport-5.0.2/lib/active_support/cache.rb:398:in `block in write' 
/Users/davea/.rvm/gems/ruby-2.4.0/gems/activesupport-5.0.2/lib/active_support/cache.rb:562:in `block in instrument' 
/Users/davea/.rvm/gems/ruby-2.4.0/gems/activesupport-5.0.2/lib/active_support/notifications.rb:166:in `instrument' 
/Users/davea/.rvm/gems/ruby-2.4.0/gems/activesupport-5.0.2/lib/active_support/cache.rb:562:in `instrument' 
/Users/davea/.rvm/gems/ruby-2.4.0/gems/activesupport-5.0.2/lib/active_support/cache.rb:396:in `write' 
/Users/davea/.rvm/gems/ruby-2.4.0/gems/activesupport-5.0.2/lib/active_support/cache.rb:596:in `save_block_result_to_cache' 
/Users/davea/.rvm/gems/ruby-2.4.0/gems/activesupport-5.0.2/lib/active_support/cache.rb:300:in `fetch' 
/Users/davea/Documents/workspace/myproject/app/helpers/webpage_helper.rb:116:in `get_cached_content' 
/Users/davea/Documents/workspace/myproject/app/helpers/webpage_helper.rb:73:in `get_url' 
/Users/davea/Documents/workspace/myproject/app/services/abstract_my_object_finder_service.rb:29:in `process_data' 
/Users/davea/Documents/workspace/myproject/app/services/run_crawlers_service.rb:26:in `block (2 levels) in run_all_crawlers' 
/Users/davea/.rvm/gems/ruby-2.4.0/gems/concurrent-ruby-1.0.5/lib/concurrent/executor/ruby_thread_pool_executor.rb:348:in `run_task' 
/Users/davea/.rvm/gems/ruby-2.4.0/gems/concurrent-ruby-1.0.5/lib/concurrent/executor/ruby_thread_pool_executor.rb:337:in `block (3 levels) in create_worker' 
/Users/davea/.rvm/gems/ruby-2.4.0/gems/concurrent-ruby-1.0.5/lib/concurrent/executor/ruby_thread_pool_executor.rb:320:in `loop' 
/Users/davea/.rvm/gems/ruby-2.4.0/gems/concurrent-ruby-1.0.5/lib/concurrent/executor/ruby_thread_pool_executor.rb:320:in `block (2 levels) in create_worker' 
/Users/davea/.rvm/gems/ruby-2.4.0/gems/concurrent-ruby-1.0.5/lib/concurrent/executor/ruby_thread_pool_executor.rb:319:in `catch' 
/Users/davea/.rvm/gems/ruby-2.4.0/gems/concurrent-ruby-1.0.5/lib/concurrent/executor/ruby_thread_pool_executor.rb:319:in `block in create_worker' 

爲了能夠將這些對象存儲在緩存中，我需要做些什麼？

Answer 1

用戶引入nokogiri的序列化功能：

$cache = ActiveSupport::Cache::MemoryStore.new 
noko_object = Nokogiri::HTML::Document.new 

serial = noko_object.serialize 
$cache.write(url, serial) 
// Serialized Nokogiri document is now in store at the URL key. 
result = $cache.read(url) 

noko_object = Nokogiri::HTML::Document.new(result) 
// noko_object is now the original document again :) 

Check out the documentation here for more information。

Answer 2

將xml存儲爲字符串，而不是對象，並在您將它們從緩存中取出後解析它們。

編輯：迴應置評

緩存這個代替

nokogiri_object.to_xml 

EDIT2：迴應置評。沿着這條線的東西。如果您想獲得更具體的幫助，您需要發佈更多的代碼。

nokogiri_object = Nokogiri::XML(cache.fetch('xml_doc')) 

編輯3：'謝謝，但是什麼是「在緩存中存儲序列化對象」代碼？我認爲「$ cache.fetch（url）{」的主體會負責存儲和檢索內容？

cache.write('url', xml_or_serialized_nokogiri_string)