What do you mean by classmethod? can you give an example?

[KimSia Sim]

You wrote here https://django-model-values.readthedocs.io/en/latest/example.html#table-logic

Table logic

Django recommends model methods for row-level functionality, and custom managers for table-level functionality. That’s fine if the custom managers are reused across models, but often they’re just custom filters, and specific to a model. As evidenced by django-model-utils’ QueryManager and PassThroughManager.

There’s a simpler way to achieve the same end: a model classmethod. In some cases a profileration of classmethods is an anti-pattern, but in this case functions won’t suffice. It’s Django that attached the Manager instance to a class.

Then you followed with an example of a classproperty.

I understand what you mean when you say custom managers are ok, if they are reused across models.

SO you're saying if there's a custom filter specific to a model, it's better off to write a classmethod.

This part I think I understand.

My question is what if it's a custom filter method specific to a model that creates new records?

Similar to get_or_create / update_or_create of the regular manager.

E.g.

from model_values import Manager as DataLayerManager

class Book(models.Model):
    data_layer = DataLayerManager # i prefer to use model_values as a separate manager keyword 

I like to have something like

Book.data_layer.create_draft(**various_parameters)

But of course the signature of create_draft is unique to Book. Do I use your classmethod suggestion?

Or alternatively, can you give an example of what you're trying to say specifically with regards to classmethod in this paragraph in the docs?

Thank you

[A. Coady]

An alternate constructor is probably the most common use of a classmethod, so I think it suits this case well. It just means the interface would be Book.create_draft instead of Book.data_layer.create_draft.

class Book(models.Model):
    data_layer = DataLayerManager()

    @classmethod
    def create_draft(cls, **...):
        cls.data_layer...

[KimSia Sim]

Thanks!