Custom field's to_python not working? - Django

Question

I'm trying to implement an encrypted char field.

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I'm using pydes for encryption

This is what I have:

from pyDes import triple_des, PAD_PKCS5
from binascii import unhexlify as unhex
from binascii import hexlify as dohex

class BaseEncryptedField(models.CharField):

    def __init__(self, *args, **kwargs):
        self.td = triple_des(unhex('c35414909168354f77fe89816c6b625bde4fc9ee51529f2f'))
        super(BaseEncryptedField, self).__init__(*args, **kwargs)

    def to_python(self, value):
        return self.td.decrypt(unhex(value), padmode=PAD_PKCS5)

    def get_db_prep_value(self, value):
        return dohex(self.td.encrypt(value, padmode=PAD_PKCS5))

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The field is saved encrypted in the database succesfully

but when retireved it does not print out the decrypted version

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Any ideas?

Answer 1

You've forgotten to set the metaclass:

class BaseEncryptedField(models.CharField):

    __metaclass__ = models.SubfieldBase

    ... etc ...

As the documentation explains, to_python is only called when the SubfieldBase metaclass is used.