Rails - Nov 2005 - Two "has_one" relationships linking to the same table?

How do i get two "has_one" relationships to the same table?

I have an audit table with fields auditor_id and manager_id that both
link to the people table:

AUDIT:
id
name
datecreated
auditor_id
manager_id

PEOPLE:
id
name

I have no idea how to link both fields from audit to people?? any
ideas??
I''m pulling my hair out trying to figure this out, please help!!

I know that if it were just one field then i''d call the field
person_id.
What do i call a second field linking to the same table ??? 
person_id_2???
please help.


Thanks,
Chris


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

Hi,

I think the trick is getting the has_many and belong_to in the correct
places. Since Audit references the People class, it is Audit that belongs to
the People. I hope I got this right way around. I think this should work
(untested code).

Class Audit < ActiveRecord::Base

belongs_to :auditor,
:class_name => "People",
:foreign_key => "auditor_id"

belongs_to :manager,
:class_name => "People",
:foreign_key => "manager_id"

end

Class People < ActiveRecord::Base

has_many :auditor_audits,
:class_name => "Audit",
:foreign_key => "auditor_id"

has_many :manager_audits,
:class_name => "Audit",
:foreign_key => "manger_id"

end


belongs_to docs:
http://api.rubyonrails.com/classes/ActiveRecord/Associations/ClassMethods.html#M000466

has_many documentation:
http://api.rubyonrails.com/classes/ActiveRecord/Associations/ClassMethods.html#M000464

-Peter


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You might want to look into single table inheritance...

example:

people
----------
id
name
type

audits
----------
id
auditor_id
manager_id

class Person < ActiveRecord::Base
end

class Auditor < Person
has_many :audits
# auditor specific functionality
end

class Manager < Person
has_many :audits
#manager specific functionality
end

class Audit < ActiveRecord
belongs_to :auditor
belongs_to :manager
end

bob = Manager.create(:name => "Bob")
joe = Auditor.create(:name => "Joe")
Audit.create(:manager_id => bob.id <http://bob.id>, :auditor_id =>
joe.id<http://joe.id>
)
...
audit = Audit.find(1)
puts audit.manager # ==> bob
puts audit.auditor # ==> joe
...
puts bob.audits
puts joe.audits

On 11/19/05, Peter Michaux
<petermichaux-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
>
> Hi,
>
> I think the trick is getting the has_many and belong_to in the correct
> places. Since Audit references the People class, it is Audit that belongs
to
> the People. I hope I got this right way around. I think this should work
> (untested code).
>
> Class Audit < ActiveRecord::Base
>
> belongs_to :auditor,
> :class_name => "People",
> :foreign_key => "auditor_id"
>
> belongs_to :manager,
> :class_name => "People",
> :foreign_key => "manager_id"
>
> end
>
> Class People < ActiveRecord::Base
>
> has_many :auditor_audits,
> :class_name => "Audit",
> :foreign_key => "auditor_id"
>
> has_many :manager_audits,
> :class_name => "Audit",
> :foreign_key => "manger_id"
>
> end
>
>
> belongs_to docs:
>
http://api.rubyonrails.com/classes/ActiveRecord/Associations/ClassMethods.html#M000466
>
>
> has_many documentation:
>
http://api.rubyonrails.com/classes/ActiveRecord/Associations/ClassMethods.html#M000464
>
>
> -Peter
> _______________________________________________
> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
>
>

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Chris Hall wrote:
> You might want to look into single table inheritance...
>
> example:
>
> people
> ----------
> id
> name
> type
>
> audits
> ----------
> id
> auditor_id
> manager_id
>
> class Person < ActiveRecord::Base
> end
>
> class Auditor < Person
>   has_many :audits
>   # auditor specific functionality
> end
>
> class Manager < Person
>   has_many :audits
>   #manager specific functionality
> end
>
Not going to cut it.  This logically implies that a person can be an 
Auditor or a Manager but not both and identifes them in the Person 
record (by the mandatory ''type'' field for STI.

Why not just:

class Audit < ActiveRecord::Base
  has_one :auditor, :foreign_key => ''auditor_id'',
:class_name => ''Person''
  has_one :manager, :foreign_key => ''manager_id'',
:class_name => ''Person''
end