时间问题？加载 yml 文件：未定义方法“keys”；对于 nil:NilClass

Question

我正在执行一个 rake 任务，该任务在我的服务器上失败，但在我的开发计算机上失败。本质上，我已经能够将问题查明到这一行：

yaml = YAML::load(File.open('somefile.yml'))

当我运行 rake 任务时，我在服务器上收到此错误：

undefined method `keys' for nil:NilClass`

在我的开发计算机上，它可以很好地完成其余代码。我四处搜寻，但找不到有关此特定事物的任何信息，但我有一种感觉，这是某种时间问题。

我也尝试过此操作，但在 YAML::load 行中遇到相同的错误：

File.open('somefile.yml', 'r') do |f|
  YAML::load(f)
  ...
end

• 如果是计时问题：如何等待文件在让 YAML 加载之前加载？
• 如果不是时间问题：可能是什么问题？

更新：

这是完整的堆栈跟踪：

[ramon@amplify current]$ rake import:test_blog RAILS_ENV=production --trace
(in /var/www/amplify/releases/20110214164531)
DEPRECATION WARNING: Rake tasks in /var/www/amplify/releases/20110214164531/vendor/plugins/acts_as_containable/tasks/acts_as_containable_tasks.rake are deprecated. Use lib/tasks instead. (called from /var/www/amplify/releases/20110214164531/Rakefile:7)
DEPRECATION WARNING: Rake tasks in /var/www/amplify/releases/20110214164531/vendor/plugins/backup_fu/tasks/backup_fu_tasks.rake are deprecated. Use lib/tasks instead. (called from /var/www/amplify/releases/20110214164531/Rakefile:7)
** Invoke import:test_blog (first_time)
** Invoke environment (first_time)
** Execute environment
** Execute import:test_blog
#<File:/var/www/amplify/releases/20110214164531/test_blog_entries.yml>
rake aborted!
undefined method `keys' for nil:NilClass
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/activerecord-3.0.1/lib/active_record/base.rb:1501:in `attribute_names'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/activerecord-3.0.1/lib/active_record/base.rb:1558:in `attributes'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/activerecord-3.0.1/lib/active_record/attribute_methods.rb:57:in `attribute_method?'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/activemodel-3.0.1/lib/active_model/attribute_methods.rb:394:in `match_attribute_method?'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/activemodel-3.0.1/lib/active_model/attribute_methods.rb:393:in `each'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/activemodel-3.0.1/lib/active_model/attribute_methods.rb:393:in `match_attribute_method?'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/activemodel-3.0.1/lib/active_model/attribute_methods.rb:378:in `respond_to?'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/activerecord-3.0.1/lib/active_record/attribute_methods.rb:52:in `respond_to?'
/home/ramon/.rvm/rubies/ree-1.8.7-2010.02/lib/ruby/1.8/yaml.rb:133:in `transfer'
/home/ramon/.rvm/rubies/ree-1.8.7-2010.02/lib/ruby/1.8/yaml.rb:133:in `node_import'
/home/ramon/.rvm/rubies/ree-1.8.7-2010.02/lib/ruby/1.8/yaml.rb:133:in `load'
/home/ramon/.rvm/rubies/ree-1.8.7-2010.02/lib/ruby/1.8/yaml.rb:133:in `load'
/var/www/amplify/releases/20110214164531/lib/tasks/test_import_export.rake:8
/var/www/amplify/releases/20110214164531/lib/tasks/test_import_export.rake:6:in `open'
/var/www/amplify/releases/20110214164531/lib/tasks/test_import_export.rake:6
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/rake-0.8.7/lib/rake.rb:636:in `call'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/rake-0.8.7/lib/rake.rb:636:in `execute'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/rake-0.8.7/lib/rake.rb:631:in `each'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/rake-0.8.7/lib/rake.rb:631:in `execute'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/rake-0.8.7/lib/rake.rb:597:in `invoke_with_call_chain'
/home/ramon/.rvm/rubies/ree-1.8.7-2010.02/lib/ruby/1.8/monitor.rb:242:in `synchronize'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/rake-0.8.7/lib/rake.rb:590:in `invoke_with_call_chain'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/rake-0.8.7/lib/rake.rb:583:in `invoke'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/rake-0.8.7/lib/rake.rb:2051:in `invoke_task'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/rake-0.8.7/lib/rake.rb:2029:in `top_level'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/rake-0.8.7/lib/rake.rb:2029:in `each'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/rake-0.8.7/lib/rake.rb:2029:in `top_level'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/rake-0.8.7/lib/rake.rb:2023:in `top_level'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/rake-0.8.7/lib/rake.rb:2001:in `run'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/rake-0.8.7/lib/rake.rb:1998:in `run'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/gems/rake-0.8.7/bin/rake:31
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/bin/rake:19:in `load'
/home/ramon/.rvm/gems/ree-1.8.7-2010.02@rails3/bin/rake:19

这是 rake 任务：

namespace :import do
  desc 'Import the entries of test blog'
  task :test_blog => :environment do
    File.open("#{Rails.root}/test_blog_entries.yml", 'r') do |file|
      p file.inspect
      yaml = YAML::load(file)
      site = Site.find_by_subdomain("test")
      blog_page = site.pages.find_by_permalink("blog")
      yaml.each do |o|
        attr = o.ivars["attributes"]
        entry = blog_page.children.new attr
        #entry.save
        puts %Q(Just created "#{entry.name}" page)
      end
    end
  end
end

namespace :export do
  desc 'Export the entries of test blog'
  task :test_blog => :environment do
    test = Site.find_by_subdomain "kish"
    entries = test.pages.find_by_permalink("blog").children
    File.open("test_blog_entries.yml", "w") do |f|
      f.puts entries.to_yaml
    end
  end
end

谢谢！

Answer 1

我发现有人有类似的问题。如果导出整个模型，YAML 似乎会阻塞 我就是这么做的，这家伙也是这么做的。所以我只导出属性，错误就消失了。