Rails：无法破坏关联

时间：2011-07-18 13:56:30

标签： ruby-on-rails

在我的应用中，用户和对话通过has_many：through关系绑定，关联表为conversation_users。

如何从对话控制器中删除关联（用户离开对话）？我试过了：

def destroy_assoc 
    Conversation.find(params[:id]).conversation_users.find_by_user_id(current_user.id).destroy
    redirect_to :back
end

但我收到undefined method 'eq' for nil:NilClass错误。当我调用该操作时，这是日志：

Processing by ConversationsController#destroy_assoc as HTML
  Parameters: {"authenticity_token"=>"8AT1wx5MUVz1Gsqpp+u+z0vk8uj4F0mAWz5wpn+CjCU=", "username"=>"albert", "id"=>"14"}
  User Load (0.2ms)  SELECT "users".* FROM "users" WHERE "users"."id" = 8 LIMIT 1
  Conversation Load (0.2ms)  SELECT "conversations".* FROM "conversations" WHERE "conversations"."id" = 14 LIMIT 1
  ConversationUser Load (0.2ms)  SELECT "conversation_users".* FROM "conversation_users" WHERE "conversation_users"."user_id" = 8 AND ("conversation_users".conversation_id = 14) LIMIT 1
Completed 500 Internal Server Error in 109ms

NoMethodError (undefined method 'eq' for nil:NilClass):
  app/controllers/conversations_controller.rb:34:in `destroy_assoc'

Rendered /Library/Ruby/Gems/1.8/gems/actionpack-3.0.9/lib/action_dispatch/middleware/templates/rescues/_trace.erb (1.0ms)
Rendered /Library/Ruby/Gems/1.8/gems/actionpack-3.0.9/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb (7.1ms)
Rendered /Library/Ruby/Gems/1.8/gems/actionpack-3.0.9/lib/action_dispatch/middleware/templates/rescues/diagnostics.erb within rescues/layout (12.9ms)

找到记录，但destroy会引发错误。我做错了什么？

感谢。

完整堆栈跟踪：

activesupport (3.0.9) lib/active_support/whiny_nil.rb:48:in `method_missing'
activerecord (3.0.9) lib/active_record/persistence.rb:83:in `destroy'
activerecord (3.0.9) lib/active_record/locking/optimistic.rb:110:in `destroy'
activerecord (3.0.9) lib/active_record/callbacks.rb:256:in `destroy'
activesupport (3.0.9) lib/active_support/callbacks.rb:414:in `_run_destroy_callbacks'
activerecord (3.0.9) lib/active_record/callbacks.rb:256:in `destroy'
activerecord (3.0.9) lib/active_record/transactions.rb:235:in `destroy'
activerecord (3.0.9) lib/active_record/transactions.rb:292:in `with_transaction_returning_status'
activerecord (3.0.9) lib/active_record/connection_adapters/abstract/database_statements.rb:139:in `transaction'
activerecord (3.0.9) lib/active_record/transactions.rb:207:in `transaction'
activerecord (3.0.9) lib/active_record/transactions.rb:290:in `with_transaction_returning_status'
activerecord (3.0.9) lib/active_record/transactions.rb:235:in `destroy'
app/controllers/conversations_controller.rb:34:in `destroy_assoc'
actionpack (3.0.9) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
actionpack (3.0.9) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
actionpack (3.0.9) lib/abstract_controller/base.rb:150:in `process_action'
actionpack (3.0.9) lib/action_controller/metal/rendering.rb:11:in `process_action'
actionpack (3.0.9) lib/abstract_controller/callbacks.rb:18:in `process_action'
activesupport (3.0.9) lib/active_support/callbacks.rb:441:in `_run__2060746170__process_action__2040097307__callbacks'
activesupport (3.0.9) lib/active_support/callbacks.rb:410:in `send'
activesupport (3.0.9) lib/active_support/callbacks.rb:410:in `_run_process_action_callbacks'
activesupport (3.0.9) lib/active_support/callbacks.rb:94:in `send'
activesupport (3.0.9) lib/active_support/callbacks.rb:94:in `run_callbacks'
actionpack (3.0.9) lib/abstract_controller/callbacks.rb:17:in `process_action'
actionpack (3.0.9) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
activesupport (3.0.9) lib/active_support/notifications.rb:52:in `instrument'
activesupport (3.0.9) lib/active_support/notifications/instrumenter.rb:21:in `instrument'
activesupport (3.0.9) lib/active_support/notifications.rb:52:in `instrument'
actionpack (3.0.9) lib/action_controller/metal/instrumentation.rb:29:in `process_action'
actionpack (3.0.9) lib/action_controller/metal/rescue.rb:17:in `process_action'
actionpack (3.0.9) lib/abstract_controller/base.rb:119:in `process'
actionpack (3.0.9) lib/abstract_controller/rendering.rb:41:in `process'
actionpack (3.0.9) lib/action_controller/metal.rb:138:in `dispatch'
actionpack (3.0.9) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
actionpack (3.0.9) lib/action_controller/metal.rb:178:in `action'
actionpack (3.0.9) lib/action_dispatch/routing/route_set.rb:62:in `call'
actionpack (3.0.9) lib/action_dispatch/routing/route_set.rb:62:in `dispatch'
actionpack (3.0.9) lib/action_dispatch/routing/route_set.rb:27:in `call'
rack-mount (0.6.14) lib/rack/mount/route_set.rb:148:in `call'
rack-mount (0.6.14) lib/rack/mount/code_generation.rb:93:in `recognize'
rack-mount (0.6.14) lib/rack/mount/code_generation.rb:82:in `optimized_each'
rack-mount (0.6.14) lib/rack/mount/code_generation.rb:92:in `recognize'
rack-mount (0.6.14) lib/rack/mount/route_set.rb:139:in `call'
actionpack (3.0.9) lib/action_dispatch/routing/route_set.rb:493:in `call'
actionpack (3.0.9) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
actionpack (3.0.9) lib/action_dispatch/middleware/head.rb:14:in `call'
rack (1.2.3) lib/rack/methodoverride.rb:24:in `call'
actionpack (3.0.9) lib/action_dispatch/middleware/params_parser.rb:21:in `call'
actionpack (3.0.9) lib/action_dispatch/middleware/flash.rb:182:in `call'
actionpack (3.0.9) lib/action_dispatch/middleware/session/abstract_store.rb:149:in `call'
actionpack (3.0.9) lib/action_dispatch/middleware/cookies.rb:302:in `call'
activerecord (3.0.9) lib/active_record/query_cache.rb:32:in `call'
activerecord (3.0.9) lib/active_record/connection_adapters/abstract/query_cache.rb:28:in `cache'
activerecord (3.0.9) lib/active_record/query_cache.rb:12:in `cache'
activerecord (3.0.9) lib/active_record/query_cache.rb:31:in `call'
activerecord (3.0.9) lib/active_record/connection_adapters/abstract/connection_pool.rb:354:in `call'
actionpack (3.0.9) lib/action_dispatch/middleware/callbacks.rb:46:in `call'
activesupport (3.0.9) lib/active_support/callbacks.rb:416:in `_run_call_callbacks'
actionpack (3.0.9) lib/action_dispatch/middleware/callbacks.rb:44:in `call'
rack (1.2.3) lib/rack/sendfile.rb:107:in `call'
actionpack (3.0.9) lib/action_dispatch/middleware/remote_ip.rb:48:in `call'
actionpack (3.0.9) lib/action_dispatch/middleware/show_exceptions.rb:47:in `call'
railties (3.0.9) lib/rails/rack/logger.rb:13:in `call'
rack (1.2.3) lib/rack/runtime.rb:17:in `call'
activesupport (3.0.9) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
rack (1.2.3) lib/rack/lock.rb:11:in `call'
rack (1.2.3) lib/rack/lock.rb:11:in `synchronize'
rack (1.2.3) lib/rack/lock.rb:11:in `call'
actionpack (3.0.9) lib/action_dispatch/middleware/static.rb:30:in `call'
railties (3.0.9) lib/rails/application.rb:168:in `call'
railties (3.0.9) lib/rails/application.rb:77:in `send'
railties (3.0.9) lib/rails/application.rb:77:in `method_missing'
railties (3.0.9) lib/rails/rack/log_tailer.rb:14:in `call'
rack (1.2.3) lib/rack/content_length.rb:13:in `call'
rack (1.2.3) lib/rack/handler/webrick.rb:52:in `service'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/httpserver.rb:104:in `service'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/httpserver.rb:65:in `run'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:173:in `start_thread'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:162:in `start'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:162:in `start_thread'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:95:in `start'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:92:in `each'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:92:in `start'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:23:in `start'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/webrick/server.rb:82:in `start'
rack (1.2.3) lib/rack/handler/webrick.rb:13:in `run'
rack (1.2.3) lib/rack/server.rb:217:in `start'
railties (3.0.9) lib/rails/commands/server.rb:65:in `start'
railties (3.0.9) lib/rails/commands.rb:30
railties (3.0.9) lib/rails/commands.rb:27:in `tap'
railties (3.0.9) lib/rails/commands.rb:27
script/rails:6:in `require'
script/rails:6

2 个答案:

答案 0 :(得分：2)

检查这个问题的答案：

undefined method `eq' for nil:NilClass with rails 3 and ruby enterprise on ubuntu hardy

如果您的关联类中没有ID字段，则不会将其视为模型。您是否使用a：has_and_belongs_to_many与没有主键id的联接表关联？

答案 1 :(得分：0)

怎么样？ 
@conversation = current_user.conversation_users.find_by_conversation_id(params[:id])
@conversation.destroy

我想

User has_many :conversation_users
User has_many :conversations :through => :conversation_users

这有用吗？我认为这至少是一种更清洁的方法，让AR做这项工作。

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