django-dirtyfields 0.6

Tracking dirty fields on a Django model instance

Django Dirty Fields
===================

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Tracking dirty fields on a Django model instance.

Dirty means that there is a difference between field value in the database and the one we currently have on a model instance.

Install
=======

::

$ pip install django-dirtyfields


Usage
=====

To use ``django-dirtyfields``, you need to:

- Inherit from ``DirtyFieldMixin`` in the Django model you want to track.

::

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)

- Use one of these 2 functions to know if the instance is dirty, and get the dirty fields:
* is\_dirty()
* get\_dirty\_fields()


Example
-------

::

$ ./manage.py shell
>>> from tests.models import TestModel
>>> tm = TestModel.create(boolean=True,characters="testing")
>>> tm.is_dirty()
False
>>> tm.get_dirty_fields()
{}

>>> tm.boolean = False
>>> tm.is_dirty()
True
>>> tm.get_dirty_fields()
{'boolean': True}


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:

::

$ ./manage.py shell
>>> from tests.models import TestModel
>>> tm = TestModel.create(fkey=obj1)
>>> 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': 1}


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.


Contributing
============
If you're interested in developing it, you can launch project tests on that way:

::

$ pip install tox
$ pip install -e .
$ tox


Credits
-------

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

.. _Stack Overflow: http://stackoverflow.com/questions/110803/dirty-fields-in-django
.. _signals: http://docs.djangoproject.com/en/1.2/topics/signals/
.. _pre_save: http://docs.djangoproject.com/en/1.2/ref/signals/#django.db.models.signals.pre_save