Last active
October 25, 2023 22:08
-
-
Save dmwyatt/6627819dc26e32b0b97a to your computer and use it in GitHub Desktop.
[ModelDiffMixin: compare previous values to new values] lets you compare previous values to new values when saving Django model #django
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
from django.forms.models import model_to_dict | |
class ModelDiffMixin(object): | |
""" | |
A model mixin[1] that tracks model fields' values and provide some useful api | |
to know what fields have been changed. | |
[1] http://stackoverflow.com/questions/1355150/django-when-saving-how-can-you-check-if-a-field-has-changed | |
""" | |
def __init__(self, *args, **kwargs): | |
super(ModelDiffMixin, self).__init__(*args, **kwargs) | |
self.__initial = self._dict | |
@property | |
def diff(self): | |
d1 = self.__initial | |
d2 = self._dict | |
diffs = [(k, (v, d2[k])) for k, v in d1.items() if v != d2[k]] | |
return dict(diffs) | |
@property | |
def has_changed(self): | |
return bool(self.diff) | |
@property | |
def changed_fields(self): | |
return self.diff.keys() | |
def get_field_diff(self, field_name): | |
""" | |
Returns a diff for field if it's changed and None otherwise. | |
""" | |
return self.diff.get(field_name, None) | |
def save(self, *args, **kwargs): | |
""" | |
Saves model and set initial state. | |
""" | |
super(ModelDiffMixin, self).save(*args, **kwargs) | |
self.__initial = self._dict | |
@property | |
def _dict(self): | |
return model_to_dict(self, fields=[field.name for field in self._meta.fields]) |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment