Rails - May 2010 - Help with relations

Hello

I have the three database models: "seller", "client" and
"account". A
seller may have many clients and many accounts, but I would like to
add the constraint that given a seller and a client, only one account
may exist between them.

Is there a way to express this contraint using ActiveRecord relations?

Thanks in advance,
Andre

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andrenth-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org wrote:
> Hello
> 
> I have the three database models: "seller", "client"
and "account". A
> seller may have many clients and many accounts, but I would like to
> add the constraint that given a seller and a client, only one account
> may exist between them.
> 
> Is there a way to express this contraint using ActiveRecord relations?
Yes -- validates_uniqueness_of will do the trick -- but never rely 
solely on ActiveRecord constraints.  You need a unique index (and 
foreign key constraints) on the DB side too.
> 
> Thanks in advance,
> Andre
Best,
--
Marnen Laibow-Koser
http://www.marnen.org
marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
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Posted via http://www.ruby-forum.com/.

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On May 21, 12:20 pm, Marnen Laibow-Koser
<li...-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:
> Yes -- validates_uniqueness_of will do the trick -- but never rely
> solely on ActiveRecord constraints.  You need a unique index (and
> foreign key constraints) on the DB side too.
I am already using the validations and key constrains. I was actually
wondering about the possibility of having Active Record generate
helper methods reflecting that kind of relation.

Thanks,
Andre

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On 21 May 2010 15:49, andrenth-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
<andre.nathan-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> Hello
>
> I have the three database models: "seller", "client"
and "account". A
> seller may have many clients and many accounts, but I would like to
> add the constraint that given a seller and a client, only one account
> may exist between them.
>
> Is there a way to express this contraint using ActiveRecord relations?
Does Client belongs_to seller, and Account belongs_to seller?  If so
then you could put client and account together in one table.
Alternatively have Client has_one account and Account belongs_to
client, or the other way round.
This doesn''t work if you have HABTM relationship of course.

Colin

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