Rails - Jul 2006 - Rails associations: Easy Question requires dumb answer

***Scroll down to see the dumb quick question***

I have two Models:

class Template < ActiveRecord::Base
end

which has this migration:
/snip
      t.column :name, :string


And the other model:

class Product < ActiveRecord::Base
  has_one :template
end

with the migration:
/snip

      t.column :qty, :integer, :default => 0
      t.column :specialDescription, :string
      t.column :template_id, :integer


Finally here is my controller code:

/snip
t=Product.create(:specialDescription=>"Cleans shit",:qty=>12)
t.template=Template.find(:first)
t.save


My intention is to have several Products reference one template. But 
when I execute the above snip, I get this:

Unknown column ''templates.product_id'' in ''where
clause'': SELECT * FROM
templates WHERE (templates.product_id = 1)


Heres the dumb question:

Why didn''t that work? Obviously rails is looking in templates for a 
productid, but I told it the exact opposite, that a product has a 
templateid. WTF MATE???


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

class Template < ActiveRecord::Base
   belongs_to :product
end

?

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

brez!  !! wrote:
> class Template < ActiveRecord::Base
>    belongs_to :product
> end
> 
> ?
Same error :(

I am so confused

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

okay...

your products table has a template_id column right?

then Product belongs_to :template (the table with the *_id column is  
the one that ''belongs_to'' something else).

and you probably also want to say that Template has_many :products

Make sense?

Trevor
--
Trevor Squires
http://somethinglearned.com



On 10-Jul-06, at 9:58 PM, Jon wrote:
> brez!  !! wrote:
>> class Template < ActiveRecord::Base
>>    belongs_to :product
>> end
>>
>> ?
>
> Same error :(
>
> I am so confused
>
> -- 
> Posted via http://www.ruby-forum.com/.
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails

class Template < ActiveRecord::Base
  belongs_to :product
end

?

On 7/10/06 8:55 PM, "Jon" <root@localhost.net> wrote:
> ***Scroll down to see the dumb quick question***
> 
> I have two Models:
> 
> class Template < ActiveRecord::Base
> end
> 
> which has this migration:
> /snip
>       t.column :name, :string
> 
> 
> And the other model:
> 
> class Product < ActiveRecord::Base
>   has_one :template
> end
> 
> with the migration:
> /snip
> 
>       t.column :qty, :integer, :default => 0
>       t.column :specialDescription, :string
>       t.column :template_id, :integer
> 
> 
> Finally here is my controller code:
> 
> /snip
> t=Product.create(:specialDescription=>"Cleans
shit",:qty=>12)
> t.template=Template.find(:first)
> t.save
> 
> 
> My intention is to have several Products reference one template. But
> when I execute the above snip, I get this:
> 
> Unknown column ''templates.product_id'' in ''where
clause'': SELECT * FROM
> templates WHERE (templates.product_id = 1)
> 
> 
> Heres the dumb question:
> 
> Why didn''t that work? Obviously rails is looking in templates for
a
> productid, but I told it the exact opposite, that a product has a
> templateid. WTF MATE???
> 

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That seems so backwards... but it works.

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

Jon wrote:
> That seems so backwards... but it works.
Whoops posted too soon. I meant to Quote Trevor''s Response was the 
solution that worked for the benefit of anyone else with a similar 
problem


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

On 7/11/06, Jon <root@localhost.net> wrote:
>
> That seems so backwards... but it works.

In your case, product belongs_to template.  That means that template
has_many products.

If you have something that has_many anythings in a db schema, that table can
not include the relationship foreign_key.

If template were to include the product_id with which it is associated, that
template can only refer to one product at a time since there is only one
column.  Conversly a product could have many templates that have it''s
product_id in the product_id column of the templates table.   So in your
case you need it the other way around.

This is the way that this situation is modelled in a relational db.

In Rails, if a table includes a reference to another table, the model for
that table, belongs_to that other model.  Belongs to will look within the
models own table for the foreign key, where has_many, and has_one will look
in the assocated models table.

Does that make it any clearer or have I rambled a bit much? ;)

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