Re: [Rails] an advice on how to use associations.

On 14 December 2011 23:47, Peter Vandenabeele <peter@vandenabeele.com> wrote:
> On Wed, Dec 14, 2011 at 11:12 PM, Mauro <mrsanna1@gmail.com> wrote:
>>
>> I have these models:
>>
>> Company;
>> Categories;
>> Classifications.
>>
>> A Company has many categories and a Category has many companies.
>> A Company for each of its own categories has a Classification.
>> For example:
>> Company-1 has Category-1 and Category-2.
>> Company-1 - Category-1 has Classification-III while Company-1 -
>> Category-2 has Classification IV.
>> How can I declare associations?
>
>
> Relevant documentation is here:
>
>   http://guides.rubyonrails.org/association_basics.html
>
> (For similar results, google for "Rails Guides <term on interest>").
>
> If I understand correctly, your case would be a perfect case for
> has_many :through (and _not_ habtm) because you need
> Classification attributes on each association between a
> Company and a Category (then the Classification table is
> the association table between Company and Category).

I'm also was thinking about has_many :through.
The join model is Classification with attriìbutes like:
company_id
category_id
classification_type
classification_amount.

But if classification.amount for classification.type II change I must
change all the occurrences for company and categories where
classification.type II occurs.

I think its better to use a join table like this:
company_id
category_id
classification_id

What do you think about?

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