class Order(models.Model): date = models.DateField(auto_now_add=True) cost = models.IntegerField() user = models.ForeignKey(User, null=True, on_delete=models.CASCADE) first_name = models.CharField(max_length=150) last_name = models.CharField(max_length=150) email = models.Ema…

[image] ermantraun: I want a reference to Order in OrderProduct to mean that either HouseOrder or TakeAwayOrder can be an Order, is there any way I can do this and would it be correct? Not in any way that I would consider worth doing. This is one of those situations where you’re probably bet…

Taks, how to solve the problem with many-to-many relationship in to Product via intermediate table? Just for each model write its own relationship and create its own intermediate model (also inheriting intermediate models from the main one)? It seems to me that in such a case abstract classes would …

[image] ermantraun: (for the main Order model should not exist as a separate entity, for it will not be used anywhere) Yes it should. It’s the “target” of the many-to-many relationship with Product. [image] ermantraun: And what do you think about generic relationships in OrderProduct to …

I mean, I think it would be better to use an abstract parent Order to inherit the fields and not create a separate entity in the database (I will remove the relationships from it and move them to the child models), wouldn’t that be more correct? And could you tell me why generic relationships would …

[image] ermantraun: wouldn’t that be more correct? No it wouldn’t. The situation you’re describing is effectively the prototypal case for multi-table inheritance. [image] ermantraun: And could you tell me why generic relationships would be inappropriate? See my reply at What are the d…

[image] KenWhitesell: No it wouldn’t. The situation you’re describing is effectively the prototypal case for multi-table inheritance. Why? I don’t understand🥺

I guess I have to turn this question around. Given that Generic Foreign Keys are an anti-pattern both from the perspective of normalization of the tables and from a data-integrity perspective, what’s your alternative? Abstract models are a syntactical convenience. They don’t actually represent any…

Why create an unnecessary entity “Order” if it is not used anywhere, and I will remove its many-to-many relationship with Product, i.e. Order will only be used to avoid repeating itself in fields and directly show in the code that business logic implies that HouseOrder and TakeAwaYOrder have a commo…

[image] ermantraun: Why create an unnecessary entity “Order” if it is not used anywhere, But it is going to be used. It expresses the common attributes of a HouseOrder and a TakeAwayOrder. It allows you to manage that Order as the independent entity that it is, while allowing for the extensi…

As I understand it, I further operate on the child models, and the parent model just rolls around in the models? I didn’t understand the relationship of subtypes to parents and how they work together in multi-table inheritance. Text from doc: class Place(models.Model): name = models.CharField(…

[image] ermantraun: As I understand it, when I create Place and Restaraunt objects that have the same name and address fields, they are automatically linked or become one object? You would create one object, the child (in this case, Restaurant). You create the Restaurant with all the fields f…

Polymorphic relations between models

Using Django Using the ORM

KenWhitesell June 17, 2024, 11:32am 2

Not in any way that I would consider worth doing.

This is one of those situations where you’re probably better off using multi-table inheritance instead of an abstract base class.

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Polymorphic relations between models

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