Django Dirty Fields

Makes a Mixing available that will give you the methods:

is_dirty()

get_dirty_fields()

is_field_dirty(field_name)

original_field_value(field_name)

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.get_dirty_fields()
{}
>>> tm.boolean = False
>>> tm.is_dirty()
True
>>> tm.get_dirty_fields()
{'boolean': True}
>>> tm.characters = "have changed"
>>> tm.is_dirty()
True
>>> tm.get_dirty_fields()
{'boolean': True, 'characters': 'testing'}
>>> tm.is_field_dirty('characters')
True
>>> tm.original_field_value('characters')
u'testing'
>>> tm.save()
>>> tm.is_dirty()
False
>>> tm.get_dirty_fields()
{}
>>>

Checking foreign key fields.

By default, dirty functions are not checking foreign keys. If you want to also take these relationships into account, use check_relationship parameter:

(ve)$ ./manage.py shell
>>> from testing_app.models import TestModel
>>> tm = TestModel(fkey=obj1)
>>> tm.save()
>>> tm.is_dirty()
False
>>> tm.get_dirty_fields()
{}
>>> tm.fkey = obj2
>>> tm.is_dirty()
False
>>> tm.is_dirty(check_relationship=True)
True
>>> tm.get_dirty_fields()
{}
>>> tm.get_dirty_fields(check_relationship=True)
{'fkey': obj1}

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