[Catalyst] Foreign keys and DBIC

[Jason Kohles]

On Feb 22, 2007, at 5:29 PM, RA Jones wrote:

> Hi folks,
>
> I'm not getting it with foreign keys in DBIC. For example, table  
> users has a column called location_id, which pulls the location  
> from the locations table like so:
>
> select u.user, l.location from users u, locations l where  
> u.location_id = l.location_id
>
> A location has many users, so in DB::Location :
> __PACKAGE__->has_many(users => 'DB::User', 'location_id');
>
> No has_many/belongs_to mappings specified in DB::Users.
>
> Then, in a method in MyApp::Controller::Users :
> $c->stash->{user} = $c->model('DB::User')->find($id);
> $c->stash->{template} = 'users/view.tt2';
>
> But the rendered view just shows location_id, not location. I  
> obviously don't quite get it and have missed something here. Do I  
> have to manually map location_id to location in either M, V or C?
>
You have setup your relationships so that a location has_many users,  
and that is it, the relationship only goes one way.  If you want the  
field in DB::User to refer back to the location, you also need a  
belongs_to relationship in your user class.

> Then I read in an article called 'Catalyst vs Rails vs Django Cook  
> off' that "Catalyst's DBIC ORM supports multi-column primary keys  
> and can do relationship mapping just by reading the schema! You  
> don't even have to bother writing any has_many belongs_to  
> definitions!" Exactly what I would like to do (like  
> CDBI::Loader::Relationship? eg "a brewery produces beers"), but how  
> so with DBIC?

See DBIx::Class::Schema::Loader

-- 
Jason Kohles
email at jasonkohles.com
http://www.jasonkohles.com/
"A witty saying proves nothing."  -- Voltaire


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