import copy import datetime from django.contrib.auth.models import User from django.db import models class RevisionableModel(models.Model): base = models.ForeignKey('self', models.SET_NULL, null=True) title = models.CharField(blank=True, max_length=255) when = models.DateTimeField(default=datetime.datetime.now) def save(self, *args, force_insert=None, force_update=None, **kwargs): super().save(*args, force_insert=force_insert, force_update=force_update, **kwargs) if not self.base: self.base = self super().save(*args, **kwargs) def new_revision(self): new_revision = copy.copy(self) new_revision.pk = None return new_revision class Order(models.Model): created_by = models.ForeignKey(User, models.CASCADE) text = models.TextField() class TestObject(models.Model): first = models.CharField(max_length=20) second = models.CharField(max_length=20) third = models.CharField(max_length=20) def __str__(self): return 'TestObject: %s,%s,%s' % (self.first, self.second, self.third)