django-softdelete-it 0.1

Example

from django.db import models
from soft_delete_it.models import SoftDeleteModel


class Author(SoftDeleteModel):
    name = models.CharField(max_length=50)
    dob = models.DateField()


class Article(SoftDeleteModel):
    title = models.CharField(max_length=50)
    body = models.TextField(null=True)
    author = models.ForeignKey(Author, on_delete=models.CASCADE, related_name='articles')


Bob = Author.objects.create(name='bob', dob='2000-12-12')
John = Author.objects.create(name='john', dob='1990-10-12')

Author.objects.all() # return QuerySet with 2 objects
Bob.delete() # Bob is soft-deleted
Author.objects.all() # return QuerySet with 1 object, John
Author.all_objects.all() # return QuerySet with 2 object, Bob and John
Bob.undelete() # un-deletes Bob object
Author.objects.all() # return QuerySet with 2 objects


article1 = Article(title='Bob The Builder', body='')
article1.author = Bob
article1.save()

Article.objects.all() # return QuerySet with 1 object, article1

Bob.delete() # soft-deletes both Bob and article1 as Article's author field is on_delete_cascade and it Inherits SoftDeleteModel

If you are implementing a new Manager for a model, simply inherit SoftDeleteManager as well along with other Managers.

If you are implementing a new QuerySet for a model, you will need to do following:

1. Inherit SoftDeleteQuerySet

2. Write Manager inheriting SoftDeleteManager which defines soft-delete functionality in it’s __init__() method(as in the example) and override get_queryset() method(as in the example)

3. Write model class inheriting SoftDeleteModel and uses above new defined Manager method(as in the example)

Example with QuerySet

Lets create a QuerySet for Article such that if no author is provided while creating a new article, one default author will be added in object.

#Creating a default author object first
default_author = Author.objects.create(name='default')

#Implementing QuerySet
from soft_delete_it.models import SoftDeleteModel, SoftDeleteQuerySet, SoftDeleteManager

class ArticleQuerySet(SoftDeleteQuerySet):

    def create(self, **kwargs):
        try:
            author = kwargs['author']
        except KeyError:
            kwargs['author'] = Author.objects.get(name='default')
        article = super(ArticleQuerySet, self).create(**kwargs)
        return article

class ArticleManager(SoftDeleteManager):

    def __init__(self, *args, **kwargs):
        self.deleted_also = kwargs.get('deleted_also', False)
        super(ArticleManager, self).__init__(*args, **kwargs)

    def get_queryset(self):
        '''return all unsoft-deleted objects'''
        if self.deleted_also:
            return ArticleQuerySet(self.model)
        return ArticleQuerySet(self.model).filter(deleted=None)

class Article(SoftDeleteModel):
    title = models.CharField(max_length=50)
    body = models.TextField(null=True)
    author = models.ForeignKey(Author, on_delete=models.CASCADE, related_name='articles')

    objects = ArticleManager.from_queryset(ArticleQuerySet)()
    all_objects = ArticleManager.from_queryset(ArticleQuerySet)(deleted_also=True)

How soft-deletion functionality is implemented:

1. Create a new soft_delete app, whole code for soft-deletion functionality is implemented in its models.py file.

2. An abstract SoftDeleteModel added which contains a deleted attribute which is a UUIDField. It will hold None for undeleted object and a new uuid4 for deleted objects.

3. SoftDeleteQuerySet implemented to override default django’s delete method to soft-delete objects instead of hard deleting them.

4. undelete(), hard_delete(), only_deleted() methods are implemented in same QuerySet class to provide extra features.

5. SoftDeleteManger implemented to use above QuerySet by overriding get_queryset() method.

6. QuerySet’s delete method is necessary to override to support bulk_delete feature.

7. Call pre_delete and post_delete signals before and after the definition of above delete method.

8. Use NestedObjects from django admin utils to soft-delete all related objects.

9. Two managers, objects and all_objects to return undeleted, all objects are implemented.