On Apr 20, 2010, at 7:06 PM, Rhett wrote: > I've run into some difficulty getting the ORM to fit into an existing > code base with some, I suppose, non-standard conventions. > > One of the conventions is to not allow primary keys (auto-incremented > integers) to be exposed on the front-end servlet or template > but to maintain the original integer values inside 'logic' or 'back- > end' code. > > We've been through a few methods of trying this, but they feel like > we're fighting sqlalchemy and must be missing something.
In Python, the closest thing we have to a "private" attribute is that it begins with an underscore. This is extremely easy to do, just name the mapped attribute "_id" or whatever name you'd like. This is documented at http://www.sqlalchemy.org/docs/mappers.html#customizing-column-properties . > The plan is to flip a flag when the object passes through a pre- > defined barrier, converting these columns only when they are asked > for. > > The original implementation had us creating two columns, one of them > being a synonym which provides the encryption > behavior, but this means we have class that look like this: > class Foo(Base): > id, _id = build_id_column(Integer, primary_key=True) where does "encryption" come into play ? are you trying to just expose the "primary key" value as something else ? easy enough, just use a descriptor: class MyClass(object): def encrypted_id(self): return encrypt_my_id(self._super_secret_id_attribute) def set_encrypted_id(self, id): self._super_secret_id_attribute = unencrypt_id(id) encrypted_id = property(encrypted_id, set_encrypted_id) mapper(MyClass, mytable, properties={ '_super_secret_id_attribute':mytable.c.id }) if you want MyClass.encrypted_id to be available in queries at the class level, this would require a SQL function that does your "encryption". See examples/derived_attributes/ for some techniques on that. -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
