Rails - Apr 2006 - has_one not using the pk?

Hello,

im trying to wrap a fairly ugly legacy schema using AR. How to handle
normalized informations which aren''t connected via the pk?

create table what (
  myid int,
  myclass int, ;; references blahclass.blahid
  mygender int
)

create table blahclass (
  blahid int,
  mdesc1 text,
  fdesc1 text)
)

I would like to wrap this as

class What < AR::Base
  has_one :blahclass

class Blahclass < AR::Base
  belongs_to :who

The problem is that a lookup of who.blahclass uses the who.pk to get the
Blahclass record, but it should use who.blahclass. I dont find a way to 
specify this.

Of course it would be easy to hardwire the logic into a method, but i
would like to use the normal relation wiring ....

Cheers,
Dirk

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

On Apr 7, 2006, at 8:11 AM, Dirk Vleugels wrote:
> Hello,
>
> im trying to wrap a fairly ugly legacy schema using AR. How to handle
> normalized informations which aren''t connected via the pk?
>
> create table what (
>   myid int,
>   myclass int, ;; references blahclass.blahid
>   mygender int
> )
>
> create table blahclass (
>   blahid int,
>   mdesc1 text,
>   fdesc1 text)
> )
>
> I would like to wrap this as
>
> class What < AR::Base
>   has_one :blahclass
>
> class Blahclass < AR::Base
>   belongs_to :who
>
> The problem is that a lookup of who.blahclass uses the who.pk to  
> get the
> Blahclass record, but it should use who.blahclass. I dont find a  
> way to
> specify this.
>
> Of course it would be easy to hardwire the logic into a method, but i
> would like to use the normal relation wiring ....
>
> Cheers,
> Dirk
First off, your has_one and belongs_to are backwards.  Beyond that  
you just need to specify the foreign key field:

class What < AR::Base
	belongs_to :blahclass, :foreign_key => "myclass"
end

class Blahclass < AR::Base
	has_one :what, :foreign_key => "myclass"
end


-Derrick Spell

Dirk
     > create table what (
     >   myclass int, ;; references blahclass.blahid
     >  ...
    ...
    > I would like to wrap this as
    > class What < AR::Base
    >   has_one :blahclass


It''s in the other direction (a common error):
    class What < AR::Base
        belongs_to :blahclass ...
     ...

When you read ''belongs_to'', think
''references'', ''points_to''.

For the details, check ''has_one'' and ''belongs_to
methods doc. at
http://api.rubyonrails.com/

Alain