Dirty fields in django

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I’ve found Armin’s idea very useful. Here is my variation;

class DirtyFieldsMixin(object):
    def __init__(self, *args, **kwargs):
        super(DirtyFieldsMixin, self).__init__(*args, **kwargs)
        self._original_state = self._as_dict()

    def _as_dict(self):
        return dict([(f.name, getattr(self, f.name)) for f in self._meta.local_fields if not f.rel])

    def get_dirty_fields(self):
        new_state = self._as_dict()
        return dict([(key, value) for key, value in self._original_state.iteritems() if value != new_state[key]])

Edit: I’ve tested this BTW.

Sorry about the long lines. The difference is (aside from the names) it only caches local non-relation fields. In other words it doesn’t cache a parent model’s fields if present.

And there’s one more thing; you need to reset _original_state dict after saving. But I didn’t want to overwrite save() method since most of the times we discard model instances after saving.

def save(self, *args, **kwargs):
    super(Klass, self).save(*args, **kwargs)
    self._original_state = self._as_dict()

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