Rails - Jul 2011 - Including associations with dynamic conditions

Given a school model and a student model with the school having a has_many 
relation to student:

has_many :students, :conditions => proc  { 
"year_id=#{send(:active_year_id)}" }

where active_year_id is a method defined in the school model, I''m 
encountering an error that "active_year_id is undefined" when calling:

School.where(:active => true).includes(:students)

The condition works fine when I do, say, School.where(:id => 10).students.

Only when I try to use includes do I get that error. Is that the right 
behavior. If not, what am I doing wrong and how do I fix ?

Using Rails 3.0.9, REE 1.8.7.

-- 
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To view this discussion on the web visit
https://groups.google.com/d/msg/rubyonrails-talk/-/9rsY1unEtsEJ.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en.

On 13 Jul 2011, at 20:23, Vijay Dev
<vijaydev.cse-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> Given a school model and a student model with the school having a has_many
relation to student:
> 
> has_many :students, :conditions => proc  {
"year_id=#{send(:active_year_id)}" }
> 
> where active_year_id is a method defined in the school model, I''m
encountering an error that "active_year_id is undefined" when calling:
> 
> School.where(:active => true).includes(:students)
> 
> The condition works fine when I do, say, School.where(:id =>
10).students.
> 
> Only when I try to use includes do I get that error. Is that the right
behavior. If not, what am I doing wrong and how do I fix ?
Interpolated conditions on associations have never worked with includes, since
the point would be to load all students in one go which you can''t do in
general if each one has different conditions.
For join based includes I believe this is flat out impossible. For the other
form you might be able to crowbar it in, but it feels very tricky

Fred
> 
> Using Rails 3.0.9, REE 1.8.7.
> -- 
> You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
> To view this discussion on the web visit
https://groups.google.com/d/msg/rubyonrails-talk/-/9rsY1unEtsEJ.
> To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
> To unsubscribe from this group, send email to
rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
> For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en.
-- 
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en.

Vijay Dev <vijaydev.cse@...> writes:
> 
> 
> Given a school model and a student model with the school having a has_many 
relation to student:
> 
> has_many :students, :conditions => proc  { "year_id=#{send
(:active_year_id)}" }

That smells like it belongs in a named scope on the School rather than on the 
relationship.

-- 
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk+unsubscribe@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en.

On Thu, Jul 14, 2011 at 5:53 AM, Andrew Skegg
<andrewskegg-BUHhN+a2lJ4@public.gmane.org> wrote:
> Vijay Dev <vijaydev.cse@...> writes:
>
> >
> >
> > Given a school model and a student model with the school having a
> has_many
> relation to student:
> >
> > has_many :students, :conditions => proc  { "year_id=#{send
> (:active_year_id)}" }
>
> That smells like it belongs in a named scope on the School rather than on
> the
> relationship.
>
>
I want school.students to always return students belonging to the active
year. I chose this way so that I don''t need to change too much of code.

> --
> You received this message because you are subscribed to the Google Groups
> "Ruby on Rails: Talk" group.
> To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
> To unsubscribe from this group, send email to
>
rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
> For more options, visit this group at
> http://groups.google.com/group/rubyonrails-talk?hl=en.
>
>
-- 
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en.

I think you can do this:


School.includes(:students).where({ :school => {:active => true, :id =>
10})

let me know if it work.

Ajit

-- 
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en.

Vijayakumar D <vijaydev.cse@...> writes:
> 
> 
> On Thu, Jul 14, 2011 at 5:53 AM, Andrew Skegg <andrewskegg-
BUHhN+a2lJ4-XMD5yJDbdMReXY1tMh2IBg@public.gmane.org>
wrote:
> 
> Vijay Dev <vijaydev.cse <at> ...> writes:
> >
> >
> > Given a school model and a student model with the school having a
has_many
> relation to student:
> >
> > has_many :students, :conditions => proc  { "year_id=#{send
> (:active_year_id)}" }
> That smells like it belongs in a named scope on the School rather than on
the
> relationship.
> 
> 
> I want school.students to always return students belonging to the active 
year. I chose this way so that I don''t need to change too much of code.


If my ESP is working, given:

School << ActiveRecord::Base
  has_many :students
  belongs_to :year
end

Student << ActiveRecord::Base
  belongs_to :school
  belongs_to :year
end

Year  <<  ActiveRecord::Base
  has_many :schools
  has_many :students
end

then finding students belonging to a particular year should be easy:

School.first.year.students

or closer to your example:

School.find(10).year.students

-- 
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk+unsubscribe@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en.