In the interest of anyone following this issue, I must confess that my
previous solution broke down the minute I deployed it. What was
interesting was that the `painful thing` - finding the context from
which the __set__ is called, proved an impossible task without a
framework hook.
IMHO this specific problem cannot be solved using proxy descriptors as
I did in the solution above.
So I was back at 1^2 - finding a post_db_load-hook where I can change
a field's value immediately after loading from the db. Since there is
none yet, I rolled my own and the QuerySet's iterator method seemed
the perfect spot for the hook. I added this right at the end - just
before the final "yield obj" statement in the iterator method (i.e.
django.db.models.query.QuerySet.iterator):
------------------------------------------
for field in obj._meta.fields:
if hasattr(field, 'get_db_post_load'):
setattr(obj, field.attname,
field.get_db_post_load(getattr(obj, field.attname)))
yield obj
------------------------------------------
Then, in my CharEncryptField, I did away with the proxy descriptor
(quite reluctantly, actually - gotta luv that bit of slick:) and
hooked into my new custom hook:
class CharEncryptField(models.CharField):
def encryptValue(self, value):
return ''.join([chr(ord(char)+1) for char in str(value)])
def decryptValue(self, value):
return ''.join([chr(ord(char)-1) for char in str(value)])
def get_internal_type(self):
return "CharField"
def get_db_prep_save(self, value):
value = self.encryptValue(value)
return super(CharEncryptField, self).get_db_prep_save(value)
def get_db_post_load(self, value):
value = self.decryptValue(value)
# no super method here (yet)
return value
This solved the problem with the context and looks a lot neater
`modulo` that boilerplate ;>
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