from django.forms.models import model_to_dict import django.db.models.fields.related class DiffableModel(object): """ Make it possible to diff a model. """ def __init__(self, *args, **kwargs): super(DiffableModel, self).__init__(*args, **kwargs) self.__initial = self._dict @property def diff(self): manytomanyfieldnames = [f.name for f in self._meta.many_to_many] d1 = self.__initial d2 = self._dict diffs = dict([(k, (v, d2[k])) for k, v in d1.items() if v != d2[k]]) # Foreign key lookups for k, v in diffs.items(): if type(self._meta.get_field(k)) is django.db.models.fields.related.ForeignKey: # If it's a foreign key, look up the name again on ourselves. # Since we only care about the *new* value, it's easy enough. diffs[k] = (v[0], getattr(self, k)) # Many to many lookups if hasattr(self, 'map_manytomany_for_diff'): for k, v in diffs.items(): if k in manytomanyfieldnames and k in self.map_manytomany_for_diff: # Try to show the display name instead here newvalue = getattr(self, self.map_manytomany_for_diff[k]) diffs[k] = (v[0], newvalue) return diffs def save(self, *args, **kwargs): super(DiffableModel, self).save(*args, **kwargs) self.__initial = self._dict @property def _dict(self): fields = [field.name for field in self._meta.fields] fields.extend([field.name for field in self._meta.many_to_many]) return model_to_dict(self, fields=fields)