# Understanding :through =\> ... :source =\> **URL:** \ **Category:** Rails\ **Created:** [July 18, 2007, 4:48am UTC](https://www.ruby-forum.com/t/understanding-through-source/109703 "2007-07-18T04:48:26Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![sshefer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/d9b06d/32.png) [@sshefer](https://www.ruby-forum.com/u/sshefer)\ **Post date:** [July 18, 2007, 4:48am UTC](https://www.ruby-forum.com/t/understanding-through-source/109703/1 "2007-07-18T04:48:26Z")
I’m trying to understand :through and :source with the following example. I have a User, Job, and Interview models. An interview has an interviewer and interviewee. I would like to use the User model for this and I assume I would have to use :source. Any ideas on where to get started? ---
**Author:** ![sshefer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/d9b06d/32.png) [@sshefer](https://www.ruby-forum.com/u/sshefer)\ **Post date:** [July 18, 2007, 6:15am UTC](https://www.ruby-forum.com/t/understanding-through-source/109703/2 "2007-07-18T06:15:37Z")
On 7/17/07, Shai S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > I’m trying to understand :through and :source with the following > example. > > I have a User, Job, and Interview models. An interview has an > interviewer and interviewee. I would like to use the User model for > this and I assume I would have to use :source. Any ideas on where to > get started? Where to start? Keep your user model simple. Think about what your views are going to show, and what the code should look like. Interview belongs\_to :interviewer, :class\_name =\> ‘User’ belongs\_to :interviewee, :class\_name =\> ‘User’ User has\_many :interviews This gets tricky, does this join with interviewer\_id or interviewee\_id in interviews? You probably need two different names for these joins. User has\_many :led\_interviews, :class\_name =\> ‘Interview’, :foreign\_key =\> ‘interviewer\_id’ has\_many :attended\_interviews, :class\_name =\> ‘Interview’, :foreign\_key =\> ‘interviewee\_id’ I find it’s best to write some sanity tests to confirm all this. I don’t claim that this will work… Now for the has\_many :through join: Job has\_many :interviews has\_many :interviewers, :through =\> :interviews has\_many :interviewees, :through =\> :interviews This doesn’t need a source, because it’s going to look at Interview#interviewer or Interview#interviewee by default. Has\_many :through associations are unique, they actually look at the other association (the “source” association) and use its reflection data. That’s why there’s no :class\_name or :foreign\_key option required. Here’s a simple case where :source would be used: Comment belongs\_to :user belongs\_to article Article has\_many :comments has\_many :users, :through =\> :comments In this case, you may not want to use #users. One: it may not be descriptive enough. Another reason is it may be too similar to Article#user, a belongs\_to association pointing to the Article’s author. So you can do this: Article has\_many :comments has\_many :commenters, :through =\> :comments Now you’ll get some error about ActiveRecord not finding a #commenter or #commenters association on Comment. Of course, it’s called #user instead! Article has\_many :comments has\_many :commenters, :through =\> :comments, :source =\> :user – Rick O. [http://lighthouseapp.com](http://lighthouseapp.com) [http://weblog.techno-weenie.net](http://weblog.techno-weenie.net) [http://mephistoblog.com](http://mephistoblog.com) ---
**Author:** ![sshefer](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/d9b06d/32.png) [@sshefer](https://www.ruby-forum.com/u/sshefer)\ **Post date:** [July 18, 2007, 4:45pm UTC](https://www.ruby-forum.com/t/understanding-through-source/109703/3 "2007-07-18T16:45:15Z")
:class\_name was just what I was looking for! For anyone else interested in this, there is another short write up at > **[Ruby Programming](https://www.thoughtco.com/ruby-programming-4133469)** > > Learn the Ruby programming language with simple, step-by-step tutorials.