Disappearing Associations

Jon_Wood · December 21, 2007, 4:23pm

Hi,

I'm using a belongs_to association to link two models, and having some very odd problems with it.

When I first view the page, all is well, and the associated object is loaded, however on the second view it crashes with a NoMethodError on the association (full trace is at the bottom of this e-mail).

It looks like my model is losing it's association on the second run, since the method no longer exists, if I call @model.class.belongs_to :associated_model it will run successfully every time.

This looks similar to bug 6720 in Trac, although that bug was apparently closed 10 months ago. Jon

Backtrace follows:

vendor/rails/activerecord/lib/active_record/attribute_methods.rb: 205:in `method_missing' vendor/rails/activerecord/lib/active_record/associations/ association_proxy.rb:125:in `send' vendor/rails/activerecord/lib/active_record/associations/ association_proxy.rb:125:in `method_missing' app/views/servers/index.rhtml:25:in `_run_erb_47app47views47servers47index46rhtml' app/views/servers/index.rhtml:18:in `each' app/views/servers/index.rhtml:18:in `_run_erb_47app47views47servers47index46rhtml' vendor/rails/actionpack/lib/action_view/base.rb:637:in `send' vendor/rails/actionpack/lib/action_view/base.rb:637:in `compile_and_render_template' vendor/rails/actionpack/lib/action_view/base.rb:365:in `render_template' vendor/rails/actionpack/lib/action_view/base.rb:316:in `render_file' vendor/rails/actionpack/lib/action_controller/base.rb:1100:in `render_for_file' vendor/rails/actionpack/lib/action_controller/base.rb:836:in `render_with_no_layout' vendor/rails/actionpack/lib/action_controller/layout.rb:262:in `render_without_benchmark' vendor/rails/actionpack/lib/action_controller/benchmarking.rb:51:in `render' /usr/lib/ruby/1.8/benchmark.rb:293:in `measure' vendor/rails/actionpack/lib/action_controller/benchmarking.rb:51:in `render' vendor/rails/actionpack/lib/action_controller/base.rb:1153:in `default_render' vendor/rails/actionpack/lib/action_controller/base.rb:1159:in `perform_action_without_filters' vendor/rails/actionpack/lib/action_controller/filters.rb:697:in `call_filters' vendor/rails/actionpack/lib/action_controller/filters.rb:689:in `perform_action_without_benchmark' vendor/rails/actionpack/lib/action_controller/benchmarking.rb:68:in `perform_action_without_rescue' /usr/lib/ruby/1.8/benchmark.rb:293:in `measure' vendor/rails/actionpack/lib/action_controller/benchmarking.rb:68:in `perform_action_without_rescue' vendor/rails/actionpack/lib/action_controller/rescue.rb:199:in `perform_action_without_caching' vendor/rails/actionpack/lib/action_controller/caching.rb:678:in `perform_action' vendor/rails/activerecord/lib/active_record/connection_adapters/ abstract/query_cache.rb:33:in `cache' vendor/rails/activerecord/lib/active_record/query_cache.rb:8:in `cache' vendor/rails/actionpack/lib/action_controller/caching.rb:677:in `perform_action' vendor/rails/actionpack/lib/action_controller/base.rb:524:in `send' vendor/rails/actionpack/lib/action_controller/base.rb:524:in `process_without_filters' vendor/rails/actionpack/lib/action_controller/filters.rb:685:in `process_without_session_management_support' vendor/rails/actionpack/lib/action_controller/session_management.rb: 123:in `process' vendor/rails/actionpack/lib/action_controller/base.rb:388:in `process' vendor/rails/actionpack/lib/action_controller/dispatcher.rb:171:in `handle_request' vendor/rails/actionpack/lib/action_controller/dispatcher.rb:115:in `dispatch' vendor/rails/actionpack/lib/action_controller/dispatcher.rb:126:in `dispatch_cgi' vendor/rails/actionpack/lib/action_controller/dispatcher.rb:9:in `dispatch' /usr/lib/ruby/gems/1.8/gems/mongrel-1.1.2/lib/mongrel/rails.rb:76:in `process' /usr/lib/ruby/gems/1.8/gems/mongrel-1.1.2/lib/mongrel/rails.rb:74:in `synchronize' /usr/lib/ruby/gems/1.8/gems/mongrel-1.1.2/lib/mongrel/rails.rb:74:in `process' /usr/lib/ruby/gems/1.8/gems/mongrel-1.1.2/lib/mongrel.rb:159:in `process_client' /usr/lib/ruby/gems/1.8/gems/mongrel-1.1.2/lib/mongrel.rb:158:in `each' /usr/lib/ruby/gems/1.8/gems/mongrel-1.1.2/lib/mongrel.rb:158:in `process_client' /usr/lib/ruby/gems/1.8/gems/mongrel-1.1.2/lib/mongrel.rb:285:in `run' /usr/lib/ruby/gems/1.8/gems/mongrel-1.1.2/lib/mongrel.rb:285:in `initialize' /usr/lib/ruby/gems/1.8/gems/mongrel-1.1.2/lib/mongrel.rb:285:in `new' /usr/lib/ruby/gems/1.8/gems/mongrel-1.1.2/lib/mongrel.rb:285:in `run' /usr/lib/ruby/gems/1.8/gems/mongrel-1.1.2/lib/mongrel.rb:268:in `initialize' /usr/lib/ruby/gems/1.8/gems/mongrel-1.1.2/lib/mongrel.rb:268:in `new' /usr/lib/ruby/gems/1.8/gems/mongrel-1.1.2/lib/mongrel.rb:268:in `run' /usr/lib/ruby/gems/1.8/gems/mongrel-1.1.2/lib/mongrel/configurator.rb: 282:in `run' /usr/lib/ruby/gems/1.8/gems/mongrel-1.1.2/lib/mongrel/configurator.rb: 281:in `each' /usr/lib/ruby/gems/1.8/gems/mongrel-1.1.2/lib/mongrel/configurator.rb: 281:in `run' /usr/lib/ruby/gems/1.8/gems/mongrel-1.1.2/bin/mongrel_rails:128:in `run' /usr/lib/ruby/gems/1.8/gems/mongrel-1.1.2/lib/mongrel/command.rb: 212:in `run' /usr/lib/ruby/gems/1.8/gems/mongrel-1.1.2/bin/mongrel_rails:281 vendor/rails/activesupport/lib/active_support/dependencies.rb:489:in `load' vendor/rails/activesupport/lib/active_support/dependencies.rb:489:in `load' vendor/rails/activesupport/lib/active_support/dependencies.rb:342:in `new_constants_in' vendor/rails/activesupport/lib/active_support/dependencies.rb:489:in `load' vendor/rails/railties/lib/commands/servers/mongrel.rb:64 /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:27:in `gem_original_require' /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:27:in `require' vendor/rails/activesupport/lib/active_support/dependencies.rb:496:in `require' vendor/rails/activesupport/lib/active_support/dependencies.rb:342:in `new_constants_in' vendor/rails/activesupport/lib/active_support/dependencies.rb:496:in `require' vendor/rails/railties/lib/commands/server.rb:39 script/server:3:in `require' script/server:3

Frederick_Cheung · December 21, 2007, 5:47pm

Hi,

I'm using a belongs_to association to link two models, and having some very odd problems with it.

When I first view the page, all is well, and the associated object is loaded, however on the second view it crashes with a NoMethodError on the association (full trace is at the bottom of this e-mail).

I'll bet you a beer that this stops happening in production mode or if
you turn on class caching. Whenever I've seen this it's been due to a dependencies screwup (which
include plugins that aren't reloaded referencing things that are,
using require when you should be letting Rails autoload things or
using require_dependency and generally things of that nature.

Fred

Jon_Wood · December 24, 2007, 9:58am

It does indeed disappear when caching is turned on, however that seems like a hack at best, thanks for the pointer though - I guess it's time to audit my code for requires

Thanks for the help,

Jon

Jon_Wood · December 24, 2007, 10:08am

Another update - I've just checked, and I'm not requiring anything installed I'm still getting the same symptoms.

I'm using a polymorphic association on the model causing this problem - could it be related to that?

Jon

Jon_Wood · December 24, 2007, 10:20am

Sorry to spam the list, but I'm hoping somebody will be able to piece together the clues.

My latest discovery is that whilst @server.details.cabinet.datacenter doesn't work, SpaceCabinet.find(@server.details.cabinet_id).datacenter does, so it appears it's the individual model object that is having problems, rather then all models of that type.

I'm feeling a little like I'm falling down the rabbit hole now!

Jon

Frederick_Cheung · December 24, 2007, 11:15am

Sorry to spam the list, but I'm hoping somebody will be able to piece together the clues.

My latest discovery is that whilst @server.details.cabinet.datacenter doesn't work, SpaceCabinet.find(@server.details.cabinet_id).datacenter does, so it appears it's the individual model object that is having problems, rather then all models of that type.

I'm feeling a little like I'm falling down the rabbit hole now!

It's even harder if you've doing it blind If you are persisting an object accross requests that could cause the
problem (normally the magic reload stuff would clear that for you, if
it didn't then you'd get a problem)

Fred

Jon_Wood · December 24, 2007, 11:44am

Nope - I'm not using the session at all at the moment. It's all just CRUD at the moment, other then the fact it's using polymorphics.

I've hacked in doing an extra find for now, although I'll have to find a better solution sometime, or I'm going to end up bringing down our database server once this goes live! Apologies for you having to work without source code - I'd provide more, but I've only just started working here, and I don't know what the policy on posting code to mailing lists is.

Happy Holidays, and thanks for your help,

Jon

Joshua_Hoskins · December 26, 2007, 12:36am

Any luck I am experiencing the thing. I noticed that the id attribute is not returned with the association is called All works fine in the console but no luck. not even from a debug console.

Jon_Wood · December 27, 2007, 10:25am

Thanks Karthik, I think that's done the trick - I was so busy trying to get rid of require statements I didn't think to *add* any!

Jon