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Description:

djangoloosefk 1.1.1

Version:
1.1.1
Source:
https://github.com/maykinmedia/django-loose-fk

Keywords:
ForeignKey, URL reference, decentralization, integrity

Django Loose FK handles local or remote “ForeignKey” references.
In a decentralized API landscape various providers can offer the same type of
data, while your own API also provides this. The django model field allows
you to handle this transparently and present a unified, clean Python API.

Contents

1 Features
2 Installation

2.1 Requirements
2.2 Install

3 Usage

3.1 Loaders
3.2 Local and remote urls

1 Features

Always work with Django model instances
Automatically added check constraints
Pluggable interface to fetch remote objects
Automatically supports DRF Hyperlinked serializers and serializer fields

2 Installation

2.1 Requirements

Python 3.10 or above
setuptools 30.3.0 or above
Django 3.2 or newer

2.2 Install
pip install django-loose-fk

Warning
You must also make sure ALLOWED_HOSTS is a list of actual domains, and not
a wildcard. When loose-fk gets a URL to load, it first looks up if the domain
is a local domain and if so, will load the actual local database record.

3 Usage
At the core sits a (virtual) django model field.
from django_loose_fk.fields import FkOrURLField

class SomeModel(models.Model):
name = models.CharField(max_length=100)

class OtherModel(models.Model):
local = models.ForeignKey(SomeModel, on_delete=models.CASCADE, blank=True, null=True)
remote = models.URLField(blank=True)
relation = FkOrURLField(fk_field="local", url_field="remote")
You can now create objects with either local instances or URLs:
some_local = SomeModel.objects.get()
OtherModel.objects.create(relation=some_local)

OtherModel.objects.create(relation="https://example.com/remote.json")
Accessing the attribute will always yield an instance:
>>> other = OtherModel.objects.get(id=1) # local FK
>>> other.relation
<SomeModel (pk: 1)>

>>> other = OtherModel.objects.get(id=2) # remote URL
>>> other.relation
<SomeModel (pk: None)>
In the case of a remote URL, the URL will be fetched and the JSON response used
as init kwargs for a model instance. The .save() method is blocked for
remote instances to prevent mistakes.

3.1 Loaders
Loaders are pluggable interfaces to load data. The default loader is
django_loose_fk.loaders.RequestsLoader, which depends on the requests
library to fetch the data.
You can specify a global default loader with the setting DEFAULT_LOOSE_FK_LOADER
DEFAULT_LOOSE_FK_LOADER = "django_loose_fk.loaders.RequestsLoader"
or override the loader on a per-field basis:
from django_loose_fk.loaders import RequestsLoader

class MyModel(models.Model):
...

relation = FkOrURLField(
fk_field="local",
url_field="remote",
loader=RequestsLoader()
)

3.2 Local and remote urls
If several services are hosted within the same domain, it could be tricky to separate
local and remote urls. In this case an additional setting LOOSE_FK_LOCAL_BASE_URLS can be used
to define an explicit list of allowed prefixes for local urls.
LOOSE_FK_LOCAL_BASE_URLS = [
"https://api.example.nl/ozgv-t/zaken/",
"https://api.example.nl/ozgv-t/catalogi/",
]