我正在我的rails应用程序中实现纸张跟踪功能.为了做到这一点,我在YAML中序列化对象.我有一个item_at_version方法,它基本上是YAML :: load(cached_object) – 这很好,但是我不知道为什么有时它返回未定义的类/ module _class name_.
它与“事件”,“会话”,“注释”等多个模型配合使用,但无理由似乎将数据集,评论,学生(我试图找到任何模式,没有任何运气) .
它与“事件”,“会话”,“注释”等多个模型配合使用,但无理由似乎将数据集,评论,学生(我试图找到任何模式,没有任何运气) .
我使用rails 3.2.8,ruby 1.9.3p327,psych作为YAML Engine(Psych :: Version返回1.3.4).
PS.当我在该文件的顶部添加require’model_name’时,它的作用就像一个魅力.
任何想法,我应该改变/添加,以使这项工作？
def item_at_version YAML::load(cached_object) end
但也许回溯将是有趣的：
~/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/psych/visitors/to_ruby.rb:312:in `path2class' ~/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/psych/visitors/to_ruby.rb:312:in `resolve_class' ~/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/psych/visitors/to_ruby.rb:219:in `visit_Psych_Nodes_Mapping' ~/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/psych/visitors/visitor.rb:15:in `visit' ~/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/psych/visitors/visitor.rb:5:in `accept' ~/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/psych/visitors/to_ruby.rb:20:in `accept' ~/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/psych/visitors/to_ruby.rb:238:in `visit_Psych_Nodes_Document' ~/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/psych/visitors/visitor.rb:15:in `visit' ~/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/psych/visitors/visitor.rb:5:in `accept' ~/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/psych/visitors/to_ruby.rb:20:in `accept' ~/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/psych/nodes/node.rb:35:in `to_ruby' ~/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/psych.rb:128:in `load' app/models/history_version.rb:7:in `item_at_version' app/controllers/history_controller.rb:8:in `show' actionpack (3.2.8) lib/action_controller/Metal/implicit_render.rb:4:in `send_action' actionpack (3.2.8) lib/abstract_controller/base.rb:167:in `process_action' actionpack (3.2.8) lib/action_controller/Metal/rendering.rb:10:in `process_action' actionpack (3.2.8) lib/abstract_controller/callbacks.rb:18:in `block in process_action' activesupport (3.2.8) lib/active_support/callbacks.rb:502:in `_run__1697733322876708236__process_action__1122943786273335015__callbacks' activesupport (3.2.8) lib/active_support/callbacks.rb:405:in `__run_callback' activesupport (3.2.8) lib/active_support/callbacks.rb:385:in `_run_process_action_callbacks' activesupport (3.2.8) lib/active_support/callbacks.rb:81:in `run_callbacks' actionpack (3.2.8) lib/abstract_controller/callbacks.rb:17:in `process_action' actionpack (3.2.8) lib/action_controller/Metal/rescue.rb:29:in `process_action' actionpack (3.2.8) lib/action_controller/Metal/instrumentation.rb:30:in `block in process_action' activesupport (3.2.8) lib/active_support/notifications.rb:123:in `block in instrument' activesupport (3.2.8) lib/active_support/notifications/instrumenter.rb:20:in `instrument' activesupport (3.2.8) lib/active_support/notifications.rb:123:in `instrument' actionpack (3.2.8) lib/action_controller/Metal/instrumentation.rb:29:in `process_action' actionpack (3.2.8) lib/action_controller/Metal/params_wrapper.rb:207:in `process_action' activerecord (3.2.8) lib/active_record/railties/controller_runtime.rb:18:in `process_action' actionpack (3.2.8) lib/abstract_controller/base.rb:121:in `process' actionpack (3.2.8) lib/abstract_controller/rendering.rb:45:in `process' actionpack (3.2.8) lib/action_controller/Metal.rb:203:in `dispatch' actionpack (3.2.8) lib/action_controller/Metal/rack_delegation.rb:14:in `dispatch' actionpack (3.2.8) lib/action_controller/Metal.rb:246:in `block in action' actionpack (3.2.8) lib/action_dispatch/routing/route_set.rb:73:in `call' actionpack (3.2.8) lib/action_dispatch/routing/route_set.rb:73:in `dispatch' actionpack (3.2.8) lib/action_dispatch/routing/route_set.rb:36:in `call' journey (1.0.4) lib/journey/router.rb:68:in `block in call' journey (1.0.4) lib/journey/router.rb:56:in `each' journey (1.0.4) lib/journey/router.rb:56:in `call' actionpack (3.2.8) lib/action_dispatch/routing/route_set.rb:600:in `call' actionpack (3.2.8) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call' rack (1.4.1) lib/rack/etag.rb:23:in `call' rack (1.4.1) lib/rack/conditionalget.rb:25:in `call' actionpack (3.2.8) lib/action_dispatch/middleware/head.rb:14:in `call' actionpack (3.2.8) lib/action_dispatch/middleware/params_parser.rb:21:in `call' actionpack (3.2.8) lib/action_dispatch/middleware/flash.rb:242:in `call' rack (1.4.1) lib/rack/session/abstract/id.rb:205:in `context' rack (1.4.1) lib/rack/session/abstract/id.rb:200:in `call' actionpack (3.2.8) lib/action_dispatch/middleware/cookies.rb:339:in `call' activerecord (3.2.8) lib/active_record/query_cache.rb:64:in `call' activerecord (3.2.8) lib/active_record/connection_adapters/abstract/connection_pool.rb:473:in `call' actionpack (3.2.8) lib/action_dispatch/middleware/callbacks.rb:28:in `block in call' activesupport (3.2.8) lib/active_support/callbacks.rb:405:in `_run__2589517259026276185__call__1369641113040304056__callbacks' activesupport (3.2.8) lib/active_support/callbacks.rb:405:in `__run_callback' activesupport (3.2.8) lib/active_support/callbacks.rb:385:in `_run_call_callbacks' activesupport (3.2.8) lib/active_support/callbacks.rb:81:in `run_callbacks' actionpack (3.2.8) lib/action_dispatch/middleware/callbacks.rb:27:in `call' actionpack (3.2.8) lib/action_dispatch/middleware/reloader.rb:65:in `call' actionpack (3.2.8) lib/action_dispatch/middleware/remote_ip.rb:31:in `call' bugsnag (1.2.5) lib/bugsnag/rack.rb:35:in `call' actionpack (3.2.8) lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call' actionpack (3.2.8) lib/action_dispatch/middleware/show_exceptions.rb:56:in `call' railties (3.2.8) lib/rails/rack/logger.rb:26:in `call_app' railties (3.2.8) lib/rails/rack/logger.rb:16:in `call' quiet_assets (1.0.1) lib/quiet_assets.rb:20:in `call_with_quiet_assets' actionpack (3.2.8) lib/action_dispatch/middleware/request_id.rb:22:in `call' rack (1.4.1) lib/rack/methodoverride.rb:21:in `call' rack (1.4.1) lib/rack/runtime.rb:17:in `call' activesupport (3.2.8) lib/active_support/cache/strategy/local_cache.rb:72:in `call' rack (1.4.1) lib/rack/lock.rb:15:in `call' actionpack (3.2.8) lib/action_dispatch/middleware/static.rb:62:in `call' railties (3.2.8) lib/rails/engine.rb:479:in `call' railties (3.2.8) lib/rails/application.rb:223:in `call' railties (3.2.8) lib/rails/railtie/configurable.rb:30:in `method_missing' ~/Library/Application Support/Pow/Versions/0.4.0/node_modules/nack/lib/nack/server.rb:147:in `handle' ~/Library/Application Support/Pow/Versions/0.4.0/node_modules/nack/lib/nack/server.rb:99:in `rescue in block (2 levels) in start' ~/Library/Application Support/Pow/Versions/0.4.0/node_modules/nack/lib/nack/server.rb:96:in `block (2 levels) in start' ~/Library/Application Support/Pow/Versions/0.4.0/node_modules/nack/lib/nack/server.rb:86:in `each' ~/Library/Application Support/Pow/Versions/0.4.0/node_modules/nack/lib/nack/server.rb:86:in `block in start' ~/Library/Application Support/Pow/Versions/0.4.0/node_modules/nack/lib/nack/server.rb:66:in `loop' ~/Library/Application Support/Pow/Versions/0.4.0/node_modules/nack/lib/nack/server.rb:66:in `start' ~/Library/Application Support/Pow/Versions/0.4.0/node_modules/nack/lib/nack/server.rb:13:in `run' ~/Library/Application Support/Pow/Versions/0.4.0/node_modules/nack/bin/nack_worker:4:in `<main>'
解决方法
当您使用YAML.dump序列化Ruby中的对象时,类名称将用作Yaml标记的一部分,以便在加载对象时可以使用正确的类.例如：
require 'yaml' class Foo; end puts YAML.dump Foo.new
产生
--- !ruby/object:Foo {}
当您在该字符串上使用YAML.load时,Psych知道为反序列化对象实例化什么类.
如果您尝试在指定未定义的类的Yaml字符串中调用YAML.load,那么您将收到错误：
require 'yaml'
# No Bar class has been defined
YAML.load '--- !ruby/object:Bar {}'
生产：
/Users/matt/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/psych/visitors/to_ruby.rb:312:in `path2class': undefined class/module Bar (ArgumentError)
from /Users/matt/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/psych/visitors/to_ruby.rb:312:in `resolve_class'
...
这是因为Psych需要创建一个类Bar的实例,但没有可用类的定义.这解释了为什么在加载Yaml之前添加需要“任何东西” – 现在Ruby已经加载了类的定义,因此可以创建它的一个实例(请注意,Ruby中的类名和文件名之间没有明确的链接,只是惯例).
因此,解决方案是确保当您从Yaml加载任何Ruby对象时,您已经需要可能包含任何可能在该Yaml中的任何类的定义的任何文件.