Hi Colin,
After reading the API, I think that
validates_presence_of :user_id
will not even check to make sure that the user exists in the user
table. It only makes sure that the field value is not blank:
http://apidock.com/rails/ActiveRecord/Validations/ClassMethods/validates_presence_of.
So this validation does not do the work of a proper foreign key
constraint. Am I reading the API incorrectly?
Thanks.
On Jul 4, 2:14 am, Colin Law <[email protected]> wrote:
> 2009/7/4 Learn by Doing <[email protected]>:
>
>
>
>
>
> > If I have
>
> > belongs_to :user
>
> > Do I need to have
>
> > validates_presence_of :user_id
>
> > ?
>
> > Does Rails validate the presence of :user_id automatically if I have
> > belongs_to :user?
>
> > In other words, does Rails prevent against creating orphan records that
> > belong to non-existent users?
>
> I believe rails will not stop you creating a record with an empty
> user_id. To be pedantic this is 'does not belong to any user' rather
> than 'belongs to a non-existent user' (for a non-existent user the
> user_id would contain a non-nil value for which there is no user). In
> some applications this is a valid requirement. If you wish to prevent
> this then include validates_presence_of as you have indicated.
>
> Colin
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