johnsu01 wrote:
>Using trunk, I have a model that has a number of fields which are
>CharFields, that I would like to be optional but if they are filled
>out, unique.
>
>
I may be well wrong but I don't think you can express this at DB level.
Uniqueness at DB level includes empty value (even NULL) as any other.
Hence you can have only one NULL, only one '', and only one 'anything
else'...
But you can teach Django to check such thing itself by writing a validator.
from django.core import validators
from django import models
class NullOrUnique:
def __init__(self, app_name, model_name, field_name):
self.app_name, self.model_name self.field_name = app_name,
model_name, field_name
def __call__(self, field_data, all_data):
if field_data is not None:
model = models.get_module(self.app_name, self.model_name)
if model.get_list(**{'self.field_name'+'__exact':field_data})
raise validators.ValidatorError('Should be null or unique')
# ...
class MyModel(meta.Model):
tab = meta.CharField(maxlength=15, validator_list =
[NullOrUnique('app_name','mymodels','tab')])
I didn't test it but the idea should be clear.
Also I think there is a better way of getting model and field name
instead of repeating them in parameters but I didn't want to dig that
far :-)
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