# Still Having Problems With :through When Going To Same Table **URL:** \ **Category:** Rails\ **Created:** [November 7, 2006, 10:53am UTC](https://www.ruby-forum.com/t/still-having-problems-with-through-when-going-to-same-table/74722 "2006-11-07T10:53:47Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![johnk](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/59ef9b/32.png) [@johnk](https://www.ruby-forum.com/u/johnk)\ **Post date:** [November 7, 2006, 10:53am UTC](https://www.ruby-forum.com/t/still-having-problems-with-through-when-going-to-same-table/74722/1 "2006-11-07T10:53:47Z")
I am having a problem with doing a :through that goes back to the same table. The following are my two classes: > > > > > class User \< ActiveRecord::Base has\_many :spanks has\_many :spanked, :through =\> :spanks, :source =\> :spanked\_user has\_many :was\_spanked\_by, :through =\> :spanks, :source =\> :user end class Spank \< ActiveRecord::Base belongs\_to :spanker, :class\_name =\> “User”, :foreign\_key =\> “user\_id” belongs\_to :spankee, :class\_name =\> “User”, :foreign\_key =\> “spanked\_user\_id” end db\_table:spanks id | user\_id | spanked\_user\_id | created\_at | updated\_at > > > > > I want to be able to make statemets like: john = User.find\_by\_nickname(“john”) john.spanked john.was\_spanked\_by Can I do this without using a :finder\_sql? The above does not work… but the following does: john.spanks spank = Spank.find(1) spank.spankee spank.spanker Help… help… I get the following error: ActiveRecord::HasManyThroughSourceAssociationNotFoundError:ActiveRecord::HasManyThroughSourceAssociationNotFoundError – John K. removed\_email\_address@domain.invalid [http://www.kopanas.com](http://www.kopanas.com) > **[Canadian University Software Engineering Conference - CUSEC](http://cusec.net/)** > > Canadian University Software Engineering Conference is a yearly conference created by students for students. [http://www.soen.info](http://www.soen.info) ---
**Author:** ![johnk](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/59ef9b/32.png) [@johnk](https://www.ruby-forum.com/u/johnk)\ **Post date:** [November 7, 2006, 10:55am UTC](https://www.ruby-forum.com/t/still-having-problems-with-through-when-going-to-same-table/74722/2 "2006-11-07T10:55:20Z")
John K. wrote: > I am having a problem with doing a :through that goes back to the same table. Try this… class User \< ActiveRecord::Base has\_many :spanks\_as\_spankee, :foreign\_key=\>‘spanked\_user\_id’, :class\_name =\> ‘Spank’ has\_many :spanks\_as\_spanker, :foreign\_key=\>‘user\_id’, :class\_name =\> ‘Spank’ has\_many :spanked, :through =\> :spanks\_as\_spankee has\_many :was\_spanked\_by, :through =\> :spanks\_as\_spanker end although, if it were my app, I would make some small association and column name changes as well, so that… class User \< ActiveRecord::Base has\_many :spanks\_as\_spankee, :foreign\_key=\>‘spankee\_id’, :class\_name =\> ‘Spank’ has\_many :spanks\_as\_spanker, :foreign\_key=\>‘spanker\_id’, :class\_name =\> ‘Spank’ has\_many :spankees, :through =\> :spanks\_as\_spankee has\_many :spankers, :through =\> :spanks\_as\_spanker end class Spank \< ActiveRecord::Base belongs\_to :spanker, :class\_name =\> “User”, :foreign\_key =\> “spanker\_id” belongs\_to :spankee, :class\_name =\> “User”, :foreign\_key =\> “spankee\_id” end Note: I haven’t actually tested the above, but I’ve done similar and it works great. Credit goes to Josh S. for showing me how to do self referential :throughs a while back via his blog. [http://blog.hasmanythrough.com/](http://blog.hasmanythrough.com/) ---
**Author:** ![johnk](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/59ef9b/32.png) [@johnk](https://www.ruby-forum.com/u/johnk)\ **Post date:** [November 7, 2006, 10:55am UTC](https://www.ruby-forum.com/t/still-having-problems-with-through-when-going-to-same-table/74722/3 "2006-11-07T10:55:23Z")
Jon G. wrote: > has\_many :spanked, :through =\> :spanks\_as\_spankee > has\_many :spankees, :through =\> :spanks\_as\_spankee > works great. Credit goes to Josh S. for showing me how to do self > referential :throughs a while back via his blog. > [http://blog.hasmanythrough.com/](http://blog.hasmanythrough.com/) Whoops, got an association backwards in the alternate option above. This is what I meant… class User \< ActiveRecord::Base has\_many :spanks\_as\_spankee, :foreign\_key=\>‘spankee\_id’, :class\_name =\> ‘Spank’ has\_many :spanks\_as\_spanker, :foreign\_key=\>‘spanker\_id’, :class\_name =\> ‘Spank’ has\_many :spank_ers_, :through =\> :spanks\_as\_spankee has\_many :spank_ees_, :through =\> :spanks\_as\_spanker end ---
**Author:** ![johnk](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/59ef9b/32.png) [@johnk](https://www.ruby-forum.com/u/johnk)\ **Post date:** [November 7, 2006, 10:55am UTC](https://www.ruby-forum.com/t/still-having-problems-with-through-when-going-to-same-table/74722/4 "2006-11-07T10:55:34Z")
Worked great! Thanks Jon… but now I have a couple questions for you if you don’t mind :-). 1. why is :through point to a has\_many relatioship? I thought it usually points to an object/table. 2. If I change spankers to spanked\_by it breaks… why? Thanks again for your help :-). On 11/2/06, Jon G. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > column name changes as well, so that… > > has\_many :spankees, :through =\> :spanks\_as\_spanker > end > > > – John K. removed\_email\_address@domain.invalid [http://www.kopanas.com](http://www.kopanas.com) > **[Canadian University Software Engineering Conference - CUSEC](http://cusec.net/)** > > Canadian University Software Engineering Conference is a yearly conference created by students for students. [http://www.soen.info](http://www.soen.info) ---
**Author:** ![johnk](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/59ef9b/32.png) [@johnk](https://www.ruby-forum.com/u/johnk)\ **Post date:** [November 7, 2006, 10:56am UTC](https://www.ruby-forum.com/t/still-having-problems-with-through-when-going-to-same-table/74722/5 "2006-11-07T10:56:08Z")
John K. wrote: > Josh S., or anyone else more familiar with how this technique works, can probably provide much better answers. But… 1. Yes, normally it would point directly to the join model/table. However, to do more complex stuff (like self referential has\_many :throughs), sometimes you gotta break out the magic wand and wave it with enthusiasm. 2. I just guessing, but maybe the ‘\_by’ suffix is getting some other Rails magic applied to it. Try changing it to :spanked\_bx, and see if that helps. Either way, someone more familiar than I with the Rails internals might be able to explain it.