MonitorField doesnt work on proxy models

[vosi]

Problem

class Model:
    field1 = MonitorField(monitor=field2)
    field2 = SomeField()


class ProxyModel:
    class Meta:
        proxy = True

Environment

• Django Model Utils version: 3.0.0
• Django version: 1.10.7
• Python version: 2.7
• Other libraries used, if any: ...

Code examples

our "sollution"

class CustomMonitorField(MonitorField):
     def pre_save(self, model_instance, add):
         value = now()
         previous_instance = model_instance.__class__.objects.get(pk=model_instance.pk)
         previous = self.get_monitored_value(previous_instance)
         current = self.get_monitored_value(model_instance)
         if previous != current:
             if self.when is None or current in self.when:
                 setattr(model_instance, self.attname, value)
                 self._save_initial(model_instance.__class__, model_instance)
         return super(MonitorField, self).pre_save(model_instance, add)