hi,
i'm writing a little statistical app for a django-project. everytime a
very model is saved, something's stored in the db, depending on the
model's attributes. if one of the attributes changes, I have to change
the statisitical data otherwise it would leed to inconsistency. I need
to know the old value of the attribute. how do I get it?
for example: I have a model
class AModel(models.Model):
a = models.CharField(...)
class StatisticModel(models.Model):
a_value = models.CharField(...)
a_counter = mdoels.IntegerField(...)
on post_save() of a = AModel(a='a') I select the StatisticModel with
a_value = 'a' and increase a_counter by 1. If then a is saved again
with a = 'b', I have to decrease a_counter of the StatisticModel with
a_value = 'a' by 1 and increase it by 1 on another instance.
How can I do this?
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