has_one :through belongs_to

Assuming the following model:

class Section < ActiveRecord::Base
  belongs_to :teacher
  has_many :students
end

class Teacher < ActiveRecord::Base
  has_many :sections
  has_many :students, :through => :sections
end

class Student < ActiveRecord::Base
  belongs_to :section
  has_one :teacher, :through => :section
end

When I try to access student.teacher, I get the error:
ActiveRecord::StatementInvalid: SQLite3::SQLException: no such column:
sections.section_id: SELECT "teachers".* FROM "teachers" INNER JOIN
sections ON teachers.id = sections.teacher_id WHERE
(("sections".section_id = 1))

Does anyone have any idea why it's looking for sections.section_id
instead of sections.id?

It's funny because I just had the same problem in my project.
It seems I was applying the has_to and the belongs_to on reverse.
Allow me to explain: I had two classes called Ad and TenureCategory
like this

class Ad < ActiveRecord::Base
  has_one :TenureCategory
end

class TenureCategory < ActiveRecord::Base
  belongs_to :Ad
end

when I tried to use these associations like
Ads.find(:first).TenureCategory I also got an SQL error stating that
either a column couldn't be found or an entire table. It seems like I
got it wrong from the begining and, in fact, it's more appropiate to
think that a TenureCategory has many Ads instead so I changed it like
so:

class Ad < ActiveRecord::Base
  belongs_to :TenureCategory, :foreign_key => 'id'
end

class TenureCategory < ActiveRecord::Base
  has_many :Ads
end

and now it works perfectly!
Perhaps in your case you should change the relationships about your
models or specify a foreign key to join them.
Hope I was of help

I think this is the same bug as:

http://rails.lighthouseapp.com/projects/8994/tickets/323-has_many-through-belongs_to_association-bug

Zach

Relationship names must be name of the table, which is plural.

Http://www.rubyplus.org
Free Ruby & Rails screencasts

Relationship names must be plural? How do you figure? If B
belongs_to A, you'd never say "B belongs to As." It's semantically
confusing if that's the case. I tried this with no luck.

Relationship names must be plural? How do you figure? If B
belongs_to A, you'd never say "B belongs to As." It's semantically
confusing if that's the case. I tried this with no luck.

Nope it's just wrong. has_one and belongs_to are singular by
convention (although the name of an association can be anything you
want, following the convention just saves you from having to specify
the class and foreign key explicitly

Fred

Does anyone have any idea why it's looking for sections.section_id
instead of sections.id?

has_one didn't support :through until Rails 2.1. Are you running 2.1?

Yep, I'm running the released version of 2.1.0.