This is a pluggable application for projects based on Django framework and its ORM.

This library stores fossilized revisions of objects and supports fossilized foreign keys.

INSTALLING

Just run "python setup.py install" or just put "fossil" package in PYTHONPATH.

HOW TO USE IT ON YOUR PROJECT

1. Add 'fossil' to INSTALLED_APPS of settings.py of your project

2. You can use FossilForeignKey fields as you can see below:

   from fossil.fields import FossilForeignKey

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

   class Purchase(models.Model): ... supplier = FossilForeignKey(Supplier, null=True, blank=True)

The model classe "Purchase" will work as usual, you can set Supplier object to the field 'supplier' but inside it will make a fossil revision for current version of this supplier and the relation will be made with it. Even if this object is deleted in the future, the relation will keep here with current data.

3. You can create and/or list manually fossils for objects, like below:

   from fossil.models import Fossil

   Returns a new or existing fossil for object

   new_fossil = Fossil.objects.create_for_object(my_supplier)

   Returns all fossils for a given object, ordered by creation date

   list_of_fossils = Fossil.objects.fossils_of_object(qualquer_objeto)

HOW IT WORKS

Django-fossil is stupdly simple. You don't need neither register a model class or inherit anyone.

It will make a fossil for a given object basing on its serialization and will not duplicate revisions for object with same values.

The serialization will be made using Django JSON serialization feature, but you can customize it implementing methods to serialize to string and deserialize to object, like below:

from django.utils import simplejson
from fossil.fields import FossilForeignKey

class SupplierManager(models.Manager):
    def deserialize_for_fossil(self, data):
        json = simplejson.loads(data)

        return Supplier(name=json['name'])

class Supplier(models.Model):
    objects = SupplierManager()
    name = models.CharField(max_length=100)

    def serialize_for_fossil(self):
        return simplejson.dumps({'name': self.name})

As you can see above, there are two methods, one to serialize and one to deserialize. The first one is as part of Model class and the second one is part of Manager class.

So you can use your creativity to make them as you want.