+class DiffModelMixIn:
+ # Provides useful methods for computing which objects in a model have
+ # changed. Make sure to do self._initial = self._dict in the __init__
+ # method.
+
+ # This is broken out of PlCoreBase into a Mixin so the User model can
+ # also make use of it.
+
+ @property
+ def _dict(self):
+ return model_to_dict(self, fields=[field.name for field in
+ self._meta.fields])
+
+ @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()
+
+ @property
+ def has_field_changed(self, field_name):
+ return field_name in self.diff.keys()
+
+ def get_field_diff(self, field_name):
+ return self.diff.get(field_name, None)
+
+
+class PlCoreBase(models.Model, DiffModelMixIn):