# Strange behavior of :through association **URL:** \ **Category:** Rails\ **Created:** [June 19, 2006, 8:43pm UTC](https://www.ruby-forum.com/t/strange-behavior-of-through-association/63837 "2006-06-19T20:43:01Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![arturaz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/73ab20/32.png) [@arturaz](https://www.ruby-forum.com/u/arturaz)\ **Post date:** [June 19, 2006, 8:43pm UTC](https://www.ruby-forum.com/t/strange-behavior-of-through-association/63837/1 "2006-06-19T20:43:01Z")
class Host \< ActiveRecord::Base belongs\_to :person end class House \< ActiveRecord::Base has\_many :people, :dependent =\> true has\_many :hosts, :through =\> :person end class Person \< ActiveRecord::Base belongs\_to :house has\_many :hosts, :dependent =\> true end Now when I try to do: @hosts = House.find\_by\_id(params[:namas]).hosts from my controller I get this: ActiveRecord::HasManyThroughAssociationNotFoundError in TinkloController#index Could not find the association :person in model Host RAILS\_ROOT: script/…/config/… /usr/lib/ruby/gems/1.8/gems/activerecord-1.14.2/lib/active\_record/reflection.rb:169:in `check_validity!' /usr/lib/ruby/gems/1.8/gems/activerecord-1.14.2/lib/active_record/associations/has_many_through_association.rb:6:in`initialize’ /usr/lib/ruby/gems/1.8/gems/activerecord-1.14.2/lib/active\_record/associations.rb:876:in `new' /usr/lib/ruby/gems/1.8/gems/activerecord-1.14.2/lib/active_record/associations.rb:876:in`hosts’ /usr/lib/ruby/gems/1.8/gems/activerecord-1.14.2/lib/active\_record/associations.rb:871:in `hosts' #{RAILS_ROOT}/app/controllers/tinklo_controller.rb:17:in`init\_vars’ #{RAILS\_ROOT}/app/controllers/tinklo\_controller.rb:3:in `index' /usr/lib/ruby/gems/1.8/gems/actionpack-1.12.1/lib/action_controller/base.rb:910:in`send’ /usr/lib/ruby/gems/1.8/gems/actionpack-1.12.1/lib/action\_controller/base.rb:910:in `perform_action_without_filters' /usr/lib/ruby/gems/1.8/gems/actionpack-1.12.1/lib/action_controller/filters.rb:368:in`perform\_action\_without\_benchmark’ /usr/lib/ruby/gems/1.8/gems/actionpack-1.12.1/lib/action\_controller/benchmarking.rb:69:in `perform_action_without_rescue' /usr/lib/ruby/gems/1.8/gems/actionpack-1.12.1/lib/action_controller/benchmarking.rb:69:in`measure’ /usr/lib/ruby/gems/1.8/gems/actionpack-1.12.1/lib/action\_controller/benchmarking.rb:69:in `perform_action_without_rescue' /usr/lib/ruby/gems/1.8/gems/actionpack-1.12.1/lib/action_controller/rescue.rb:82:in`perform\_action’ /usr/lib/ruby/gems/1.8/gems/actionpack-1.12.1/lib/action\_controller/base.rb:381:in `send' /usr/lib/ruby/gems/1.8/gems/actionpack-1.12.1/lib/action_controller/base.rb:381:in`process\_without\_filters’ /usr/lib/ruby/gems/1.8/gems/actionpack-1.12.1/lib/action\_controller/filters.rb:377:in `process_without_session_management_support' /usr/lib/ruby/gems/1.8/gems/actionpack-1.12.1/lib/action_controller/session_management.rb:117:in`process’ /usr/lib/ruby/gems/1.8/gems/rails-1.1.2/lib/dispatcher.rb:38:in `dispatch' /usr/lib/ruby/gems/1.8/gems/rails-1.1.2/lib/webrick_server.rb:115:in`handle\_dispatch’ /usr/lib/ruby/gems/1.8/gems/rails-1.1.2/lib/webrick\_server.rb:81:in `service' /usr/lib/ruby/1.8/webrick/httpserver.rb:104:in`service’ /usr/lib/ruby/1.8/webrick/httpserver.rb:65:in `run' /usr/lib/ruby/1.8/webrick/server.rb:172:in`start\_thread’ /usr/lib/ruby/1.8/webrick/server.rb:161:in `start' /usr/lib/ruby/1.8/webrick/server.rb:161:in`start\_thread’ /usr/lib/ruby/1.8/webrick/server.rb:95:in `start' /usr/lib/ruby/1.8/webrick/server.rb:92:in`each’ /usr/lib/ruby/1.8/webrick/server.rb:92:in `start' /usr/lib/ruby/1.8/webrick/server.rb:82:in`start’ /usr/lib/ruby/1.8/webrick/server.rb:82:in `start' /usr/lib/ruby/gems/1.8/gems/rails-1.1.2/lib/webrick_server.rb:67:in`dispatch’ /usr/lib/ruby/gems/1.8/gems/rails-1.1.2/lib/commands/servers/webrick.rb:59 /usr/local/lib/site\_ruby/1.8/rubygems/custom\_require.rb:21:in `require__' /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:21:in`require’ /usr/lib/ruby/gems/1.8/gems/activesupport-1.3.1/lib/active\_support/dependencies.rb:147:in `require' /usr/lib/ruby/gems/1.8/gems/rails-1.1.2/lib/commands/server.rb:30 /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:21:in`require\_\_’ /usr/local/lib/site\_ruby/1.8/rubygems/custom\_require.rb:21:in `require' /usr/lib/ruby/gems/1.8/gems/activesupport-1.3.1/lib/active_support/dependencies.rb:147:in`require’ script/server:3 Request Parameters: {“namas”=\>“39”} Response Headers: {“cookie”=\>[], “Cache-Control”=\>“no-cache”} Ideas? ---
**Author:** ![arturaz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/73ab20/32.png) [@arturaz](https://www.ruby-forum.com/u/arturaz)\ **Post date:** [June 19, 2006, 10:46pm UTC](https://www.ruby-forum.com/t/strange-behavior-of-through-association/63837/2 "2006-06-19T22:46:42Z")
I’m only guessing but I wonder if :through has problems with people/person as a plural. Do you also get the problem if you use a name that has a standard plural with an s added? Julian ---
**Author:** ![arturaz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/73ab20/32.png) [@arturaz](https://www.ruby-forum.com/u/arturaz)\ **Post date:** [June 19, 2006, 10:59pm UTC](https://www.ruby-forum.com/t/strange-behavior-of-through-association/63837/3 "2006-06-19T22:59:01Z")
Another thought. What is “find\_by\_id”? I can’t find this in the Rails documentation or in any source files in my Rails installation. It is mentioned in various places though according to Google. Strange. You could try using find(params[:namas]) and possible checking the result before trying for the through record. Finally, do your database tables have the correct foreign key fields (house\_id, person\_id)? Julian ---
**Author:** ![arturaz](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/73ab20/32.png) [@arturaz](https://www.ruby-forum.com/u/arturaz)\ **Post date:** [June 20, 2006, 12:10am UTC](https://www.ruby-forum.com/t/strange-behavior-of-through-association/63837/4 "2006-06-20T00:10:05Z")
ArtÅ«ras Å lajus wrote: > class Host \< ActiveRecord::Base > belongs\_to :person > end > > class House \< ActiveRecord::Base > has\_many :people, :dependent =\> true > has\_many :hosts, :through =\> :person > end > > class Person \< ActiveRecord::Base > belongs\_to :house > has\_many :hosts, :dependent =\> true > end > > Now when I try to do: > @hosts = House.find\_by\_id(params[:namas]).hosts > from my controller I get this: > ActiveRecord::HasManyThroughAssociationNotFoundError in > TinkloController#index > > Could not find the association :person in model Host You don’t have a :person has\_many to go through. Use the :people name, that’s what you declared in the previous line. Also, :dependent should be :destroy, as “true” has been deprecated as a valid option. class House \< ActiveRecord::Base has\_many :people, :dependent =\> :destroy has\_many :hosts, :through =\> :people end – Josh S. [http://blog.hasmanythrough.com](http://blog.hasmanythrough.com)