Question

This should be easy. I think I must be getting caught up on naming.

Both a ‘manager’ and a ‘subordinate’ (employee) are of class “Person”.

Here’s what I have:

class Person < ActiveRecord::Base
  has_many :person_manager_assignments
  has_many :managers, :through => :person_manager_assignments
  has_many :subordinates, :through => :person_manager_assignments
end

class PersonManagerAssignment < ActiveRecord::Base
  has_one :subordinate, :class_name => "Person", :foreign_key => "id", :primary_key => 'person_id'
  has_one :manager, :class_name => "Person", :foreign_key => "id", :primary_key => 'manager_id'
end

Which works great for checking and assigning managers.

I’m caught on the part about subordinates. It returns the Person’s self, instead of their subordinates:

p.subordinates
  Person Load (0.5ms)  SELECT "people".* FROM "people" INNER JOIN "person_manager_assignments" ON "people"."id" = "person_manager_assignments"."person_id" WHERE "person_manager_assignments"."person_id" = 15973

See the bit where in the WHERE clause where it’s matching “person_id”? I need that to be “manager_id”, but messing with the PersonManagerAssignment associations foreign_key and primary_key values doesn’t seem to help.

Any ideas?

Answer 1

Answer is essentially here: http://railscasts.com/episodes/163-self-referential-association

So I think you need this:

class Person < ActiveRecord::Base
  has_many :person_manager_assignments
  has_many :managers, :through => :person_manager_assignments
  has_many :subordinate_relationships, :class_name=>"PersonManagerAssignment", :foreign_key=>"manager_id"
  has_many :subordinates, :through => :subordinate_relationships, :source=>:person
end

and

class PersonManagerAssignment < ActiveRecord::Base
  belongs_to :person
  belongs_to :manager, :class_name=>"Person"
end

Rock on.