Re: one-to-one GenericRelation best practices

Hello,

May be you want to subclass GenericForeignKey:

class GenericOneToOne(GenericForeignKey):

    many_to_one = False

    one_to_many = False

    one_to_one = True

Though have not tried it so YMMV.

Kind regards

On Thu, May 31, 2018 at 8:59 PM, Vitor Barbosa <vitorqb@gmail.com> wrote:

Hello! This is my first question, so please excuse any mistakes.

I'm using django 1.8 (working on migration to 2.0).

I need to implement a one-to-one generic relation. To illustrate suppose I have three classes, the first representing and abstract class in a store and the other specific products which need extra information:

AbstractProduct(models.Model):

    <fields here>

    sale = GenericRelation('Sales')

    class Meta:

        abstract = True

Books(AbstractProduct):

    <fields here>

Magazines(AbstractProduct):

    <fields here>

Now I need to create a models for 'Sales'. Each sale is of a specific product. Following https://docs.djangoproject.com/en/2.0/ref/contrib/contenttypes/#generic-relations I used:

class Sales(models.Model):

    <fields here>

    content_type = models.ForeignKey(...)

    object_id = models.PositiveIntegerField(...)

    content_object = GenericForeignKey('content_type', 'object_id')

My problem is that by using this approach whenever I do

>>> Books.objects.get(pk=1).sale

I get back a manager since django does not know it is a one-to-one relation. And it makes me think that maybe I'm approaching this in the wrong way.

My question is:

(a) is this design a good solution for this problem? Is there a better approach? Has anyone solved a similar problem in a better way?

(b) is there a way to create a generic One-To-One relation?

I'm open to answers pointing to good blogs/books/articles which give a more formal approach to this kind of design issue, if you know a good one.

Thanks in advance! Yours,

Vitor.

--

Vitor Quintanilha Barbosa

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