caldwell-dirtyfields 0.5b1

Tracking dirty fields on a Django model instance

Tracking changed fields on a Django model instance.

Makes a Mixin available that will give you the properties:

• is_dirty

• dirty_fields

Installing

Install the package using pip. Then use the instructions in “Using the Mixin in the Model”.

$ pip install django-dirtyfields

or if you’re interested in developing it, use virtualenv. The default settings.py will look for the dirtyfields package in its current location.

$ virtualenv --no-site-packages ve/
$ source ve/bin/activate
(ve)$ cd example_app
(ve)$ pip install -r requirements.pip
(ve)$ ./manage.py test testing_app

Using the Mixin in the Model

from django.db import models
from dirtyfields import DirtyFieldsMixin

class TestModel(DirtyFieldsMixin, models.Model):
    """A simple test model to test dirty fields mixin with"""
    boolean = models.BooleanField(default=True)
    characters = models.CharField(blank=True, max_length=80)

Using it in the shell

(ve)$ ./manage.py shell
>>> from testing_app.models import TestModel
>>> tm = TestModel(boolean=True, characters="testing")
>>> tm.save()
>>> tm.is_dirty
False
>>> tm.dirty_fields
()
>>> tm.boolean = False
>>> tm.is_dirty
True
>>> tm.dirty_fields
('boolean', )
>>> tm.characters = "have changed"
>>> tm.is_dirty
True
>>> tm.dirty_fields
('boolean', 'characters', )
>>> tm.save()
>>> tm.is_dirty
False
>>> tm.get_dirty_fields
()

Why would you want this?

When using signals, especially pre_save, it is useful to be able to see what fields have changed or not. A signal could change its behaviour depending on whether a specific field has changed, whereas otherwise, you only could work on the event that the model’s save() method had been called.

Credits

This code has largely be adapted from what was made available at Stack Overflow.