Hi Jamu,
thanks for your fast answer. Unfortunatly, I was not really happy with
the suggested solutions. So I solved the problem differently now. I
worked around the problem by subclassing Reference in order to extend it
with validation features. I tried to be as less intrusive to the
Reference class as possible and to copy the validation mechanism for the
Variables as good as possible. It's still not filling the
validator_attribute field automatically, but nevertheless, it could also
be useful for others, so I'd like to share it:
class ValidatingReference(storm.references.Reference):
def __init__(self, *args, **kwargs):
validator = kwargs.pop('validator', None)
if validator is not None:
self._validator = validator
self._validator_attribute =
kwargs.pop('validator_attribute', None)
storm.references.Reference.__init__(self, *args, **kwargs)
def __set__(self, local, remote, from_db=False):
local = get_obj_info(local).get_obj()
remote = get_obj_info(remote).get_obj()
if self._validator and not from_db:
remote = self._validator(local,
self._validator_attribute, remote)
storm.references.Reference.__set__(self, local, remote)
Am 18.08.2011 15:00, schrieb Jamu Kakar:
Hi Michael,
On Thu, Aug 18, 2011 at 1:25 PM, Michael Löffler<[email protected]> wrote:
I'm looking for an elegant way, to validate referenced objects. Let's say, I
have a table 'persons' with the attributes 'father', 'mother', 'age', and I
want to validate for example, that the parents are actually older then their
children. So I have code like
class Person(object):
__storm_table__ = 'persons'
id = Int(primary=True)
father_id = Int()
father = Reference(id, father_id)
...
Adding a validator to the father_id attribute would have to look up the
object by the id first, and then process the validation, even if the
reference already knows the referenced object. This extra lookup would be
inefficient in my eyes. On the other side, a Reference doesn't seem to have
a validation mechanism. Would it be wise, to somehow subclass Reference, or
do I better stick with the lookup of the id? Are there any side effects I
should be aware of?
There's no great way to do this in Storm, right now. You could define
a validator for the father_id property, as you suggest, but one
concern is that creating many Person instances will run a lot of
individual queries to fetch the references. If you only create one at
a time, it's not a big deal, but if you create many instances you
probably want to write a function create_people(...) that can fetch
the related objects using a single query and perform the validation in
a batch.
Thanks,
J.
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