Rails - Apr 2006 - has_many :through with has_many/has_many join models

It seems that using a join model that joins with two has_many''s will 
fail to generate proper SQL

class StudentSemesterRecord < ActiveRecord::Base
  belongs_to :semester
  has_many :discipline_records, :through => :semester
end

class Semester < ActiveRecord::Base
  has_many :student_semester_records
  has_many :discipline_records
end

class DisciplineRecord < ActiveRecord::Base
  belongs_to :semester
end

student_semester_record.discipline_records yields this SQL:
SELECT discipline_records.* FROM discipline_records INNER JOIN semesters 
ON discipline_records.semester_id = semesters.id WHERE 
(semesters.semester_id = 1349)

The where clause is invalid. It is using:
semesters.semester_id = #{student_semester_record.id}

It should be using:
semesters.id = #{student_semester_record.semester_id}

Am I doing something wrong, is this a bug, or is this association type 
simply not supported?

Thanks!

-- 
Jack Christensen
jackc@hylesanderson.edu

Jack Christensen wrote:
> It seems that using a join model that joins with two has_many''s
will
> fail to generate proper SQL
> 
> class StudentSemesterRecord < ActiveRecord::Base
>   belongs_to :semester
>   has_many :discipline_records, :through => :semester
> end
> 
> class Semester < ActiveRecord::Base
>   has_many :student_semester_records
>   has_many :discipline_records
> end
> 
> class DisciplineRecord < ActiveRecord::Base
>   belongs_to :semester
> end
You can do a has_many :through two ways.  One is using a join model with 
two belongs_to associations. The other is to go through a model with a 
belongs_to and a has_many association. The setup you describe is 
interesting, but not currently supported.

--
Josh Susser
http://blog.hasmanythrough.com

-- 
Posted via http://www.ruby-forum.com/.

Josh Susser wrote:

Jack Christensen wrote:

It seems that using a join model that joins with two has_many''s will
fail to generate proper SQL

class StudentSemesterRecord < ActiveRecord::Base
  belongs_to :semester
  has_many :discipline_records, :through => :semester
end

class Semester < ActiveRecord::Base
  has_many :student_semester_records
  has_many :discipline_records
end

class DisciplineRecord < ActiveRecord::Base
  belongs_to :semester
end

You can do a has_many :through two ways.  One is using a join model with 
two belongs_to associations. The other is to go through a model with a 
belongs_to and a has_many association. The setup you describe is 
interesting, but not currently supported.

My fault. I was going at it the wrong way. The models are
rather extensive and I stripped a little too much out for the original
post. There is also a Person model. StudentSemesterRecord and
DisciplineRecord both belong_to Person. So it actually needn''t go
through Semester, it can search with two conditions directly on
DisciplineRecord:

  has_many :discipline_records,

           :finder_sql => ''SELECT * FROM discipline_records
WHERE
semester_id=#{semester_id} AND person_id=#{student_id}'' 

The problem is using finder_sql stops me from being able to use :order
or :conditions on find or count.

It appears I really want to use with_scope to filter to the semester
level and then use the regular has_many associations from Person.

Thanks!

Jack

--
Josh Susser
http://blog.hasmanythrough.com

-- 
Jack Christensen
jackc-/SOt/BrQZzMOf2zXYvRtkodd74u8MsAO@public.gmane.org


_______________________________________________
Rails mailing list
Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
http://lists.rubyonrails.org/mailman/listinfo/rails

Jack Christensen wrote:
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
listserv seems to have eaten your reply

--
Josh Susser
http://blog.hasmanythrough.com

-- 
Posted via http://www.ruby-forum.com/.