Rails - Dec 2006 - Class that belongs_to another Class twice?

I have Class Referral which takes both a giver and receiver as a Person.
As is, @person.referrals returns all referrals as appropriate.  Using
built in AR methods, @referral.person returns the receiver of the
referral.  To find out who issued the referral, I have created an
instance method "giver" so that @referral.giver returns the Person who
gave it.  I looked at Chad Fowler''s "Self-Referential MtM
Models" but
I''m not sure my situation is the same.  The current setup I have works,
but I''m not sure if there is a better Rails way to do this.
>MIGRATION
class CreateReferrals < ActiveRecord::Migration
  def self.up
    create_table :referrals do |t|
      t.column :giver_id, :integer, :null => false
      t.column :receiver_id, :integer, :null => false
      t.column :body, :text, :null => false
      t.column :created_at, :datetime
    end
>REFERRAL MODEL
class Referral < ActiveRecord::Base
  belongs_to :person

  validates_uniqueness_of :giver_id, :scope => :receiver_id

  def giver
    Person.find(self.giver_id)
  end
>PERSON MODEL
class Person < ActiveRecord::Base

  has_many  :referrals, :foreign_key => "receiver_id"

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On Dec 19, 2:59 pm, Taylor Strait
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
> I have Class Referral which takes both a giver and receiver as a Person.
> As is, @person.referrals returns all referrals as appropriate.  Using
> built in AR methods, @referral.person returns the receiver of the
> referral.  To find out who issued the referral, I have created an
> instance method "giver" so that @referral.giver returns the
Person who
> gave it.  I looked at Chad Fowler''s "Self-Referential MtM
Models" but
> I''m not sure my situation is the same.  The current setup I have
works,
> but I''m not sure if there is a better Rails way to do this.
>
> >MIGRATIONclass CreateReferrals < ActiveRecord::Migration
>   def self.up
>     create_table :referrals do |t|
>       t.column :giver_id, :integer, :null => false
>       t.column :receiver_id, :integer, :null => false
>       t.column :body, :text, :null => false
>       t.column :created_at, :datetime
>     end
>
> >REFERRAL MODELclass Referral < ActiveRecord::Base
>   belongs_to :person
     has_one :giver, :class_name =>
"Person"
>
>   validates_uniqueness_of :giver_id, :scope => :receiver_id
>
>   def giver
>     Person.find(self.giver_id)
>   end
>
> >PERSON MODELclass Person < ActiveRecord::Base
>
>   has_many  :referrals, :foreign_key => "receiver_id"
>
> --
> Posted viahttp://www.ruby-forum.com/.
I think you should be able to just add the has_one association to the
referral model and get your attribute accessor for free...

Best,

-r

--
Ryan Raaum
http://raaum.org
http://rails.raaum.org -- Rails docs
http://locomotive.raaum.org -- Self contained Rails for Mac OS X


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>>  REFERRAL MODELclass Referral < ActiveRecord::Base
>>    belongs_to :person
>>    has_one :giver, :class_name => "Person"
Unfortunately this does not work:
>VIEW CODE
<% for referral in @referrals %>
  <tr>
    <td>#{referral.giver.full_name}</td>
    <td><%= referral.body %></td>
  </tr>
>ERROR
Mysql::Error: #42S22Unknown column ''people.referral_id'' in
''where
clause'': SELECT * FROM people WHERE (people.referral_id = 4)  LIMIT 1

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>> has_one :giver, :class_name => "Person", :foreign_key
=> "giver_id"
I knew I should have posted that I tried that too.  Well, I tried that 
too!  The thing is that AR is doing:
>>    belongs_to :person
>>    has_one :giver, :class_name => "Person"
SELECT * FROM people WHERE (people.referral_id = 4)  LIMIT 1
>>    belongs_to :person
>>    has_one :giver, :class_name => "Person", :foreign_key
=> "giver_id"
SELECT * FROM people WHERE (people.giver_id = 4)  LIMIT 1

when it should be doing:

SELECT * FROM people WHERE (people.id = 4)  LIMIT 1

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On Dec 19, 5:12 pm, Taylor Strait
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
> >> has_one :giver, :class_name => "Person", :foreign_key
=> "giver_id"I knew I should have posted that I tried that too. 
Well, I tried that
> too!  The thing is that AR is doing:
>
> >>    belongs_to :person
> >>    has_one :giver, :class_name => "Person"SELECT *
FROM people WHERE (people.referral_id = 4)  LIMIT 1
>
> >>    belongs_to :person
> >>    has_one :giver, :class_name => "Person",
:foreign_key => "giver_id"SELECT * FROM people WHERE
(people.giver_id = 4)  LIMIT 1
>
> when it should be doing:
>
> SELECT * FROM people WHERE (people.id = 4)  LIMIT 1
>
> --
> Posted viahttp://www.ruby-forum.com/.
Ok.  Here''s what I''ve got...

## Migrations

    create_table "people" do |t|
      t.column "name", :string
    end
    create_table "referrals" do |t|
      t.column "giver_id", :integer
      t.column "receiver_id", :integer
    end

## Models

class Person < ActiveRecord::Base
  has_many :referrals, :foreign_key => "receiver_id"
end

class Referral < ActiveRecord::Base
  belongs_to :receiver, :class_name => "Person", :foreign_key =>
"receiver_id"
  belongs_to :giver, :class_name => "Person", :foreign_key =>
"giver_id"
end

## Console

r = Person.create
g = Person.create
ref = Referral.create(:giver => g, :receiver => r)

r.reload
g.reload

r.referrals #=> [ ref ]
g.referrals #=> []
ref.giver #=> g
ref.receiver #=> r

Best,

r

--
Ryan Raaum
http://raaum.org
http://rails.raaum.org -- Rails docs
http://locomotive.raaum.org -- Self contained Rails for Mac OS X


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Works great, Ryan.  Much less hackish than my original solution.  Thanks 
everyone.

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