Utility to serialize generic model instances

generic_model_instance.py

from __future__ import annotations

from typing import Any
from typing import NamedTuple

from django.contrib.contenttypes.models import ContentType
from django.db import models


class GenericModelInstance(NamedTuple):
    """Utility to avoid sending whole objects to Celery tasks."""

    content_type_id: int
    model_id: Any

    def get_instance(self) -> models.Model:
        content_type = ContentType.objects.get_for_id(self.content_type_id)
        return content_type.get_object_for_this_type(pk=self.model_id)

    @classmethod
    def from_instance(cls, instance: models.Model) -> GenericModelInstance:
        content_type = ContentType.objects.get_for_model(instance, for_concrete_model=True)
        return cls(
            content_type_id=content_type.pk,
            model_id=instance.pk,
        )