Rails - Apr 2006 - using two foreign keys to the same table

i am working on a task manager with ruby on rails. it is my first major 
project, so i''m still gettng my feet wet as i learn.

i''ve been trying to use the built in relationships to link my tables 
together, but i''m not able to use the same naming conventions. for each
task, it has a field for the creator, and another field for the 
assignee. both of these fields reference the users table. obviously i 
can''t have two fields that say user_id in my tasks table, so how do i 
get them to link right and specify a different field?

here is my current database schema:
_Tasks_
  id int not null auto_increment,
  task_name varchar(100) not null,
  description text not null,
  user_id int not null,
  assignee int not null,
  date_due date not null,
  completed_at datetime not null,
  constraint fk_task_user foreign key (user_id) references users(id),
  constraint fk_task_assignee foreign key (assignee) references 
users(id),

_Users_
  id int not null auto_increment,
  username varchar(20) not null,
  password varchar(20) not null,
  full_name varchar(100) not null,
  email varchar(150) not null,
  primary key (id)

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

Josh Kieschnick wrote:
> i am working on a task manager with ruby on rails. it is my first major
> project, so i''m still gettng my feet wet as i learn.
> 
> i''ve been trying to use the built in relationships to link my
tables
> together, but i''m not able to use the same naming conventions. for
each
> task, it has a field for the creator, and another field for the
> assignee. both of these fields reference the users table. obviously i
> can''t have two fields that say user_id in my tasks table, so how
do i
> get them to link right and specify a different field?
> 
> here is my current database schema:
> _Tasks_
>   id int not null auto_increment,
>   task_name varchar(100) not null,
>   description text not null,
>   user_id int not null,
>   assignee int not null,
>   date_due date not null,
>   completed_at datetime not null,
>   constraint fk_task_user foreign key (user_id) references users(id),
>   constraint fk_task_assignee foreign key (assignee) references
> users(id),
> 
> _Users_
>   id int not null auto_increment,
>   username varchar(20) not null,
>   password varchar(20) not null,
>   full_name varchar(100) not null,
>   email varchar(150) not null,
>   primary key (id)
> 
(This is my first reply through the Gmane gateway, let''s hope it
works...)

You don''t have to name your foreign key user_id. Rails can indeed guess
the
correct relations when you do, but you can override. From the api docs:

belongs_to :author, :class_name => "Person", :foreign_key =>
"author_id"

http://api.rubyonrails.com/classes/ActiveRecord/Associations/ClassMethods.html#M000529

You could do something like 

belongs_to :user, :foreign_key => "creator_id"
belongs_to :user, :foreign_key => "assignee_id"

>
http://api.rubyonrails.com/classes/ActiveRecord/Associations/ClassMethods.html#M000529
> 
> You could do something like
> 
> belongs_to :user, :foreign_key => "creator_id"
> belongs_to :user, :foreign_key => "assignee_id"
exactly what i was looking for. thanks.

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

On 4/6/06, Wiebe Cazemier <halfgaar@gmx.net>
wrote:
> You could do something like
>
> belongs_to :user, :foreign_key => "creator_id"
> belongs_to :user, :foreign_key => "assignee_id"
>
I doubt that will work.  Try:

belongs_to :creator, :class_name=>''User'', :foreign_key
=> "creator_id"
belongs_to :assignee, :class_name=>''User'', :foreign_key
=> "assignee_id"

Which is also untested, but more likely to work.

Jeremy Evans wrote:
> I doubt that will work.  Try:
> 
> belongs_to :creator, :class_name=>''User'', :foreign_key
=> "creator_id"
> belongs_to :assignee, :class_name=>''User'',
:foreign_key => "assignee_id"
> 
> Which is also untested, but more likely to work.
Oh yeah, whoops. The association needs a name :)