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