As the uniform all values approach has created a bit of confusion, let
me present a larger example:
Validators in core.validators should not be concerned with either
model or form internals if possible. This is currently straightforward
to achieve by passing all values always as a dict via
form.cleaned_data or model.__dict__.copy() (dict copying is cheap, the
original instance dict is unsafe to pass around).
This makes multi-field validators work uniformly for both models and
fields. Otherwise you have to always handle identical validation
differently for forms and models -- this is extremely smelly in my
opinion.
And now the example:
class RequiredIfOtherFieldEquals(object):
def __call__(self, value, all_values={}, instance=None):
if self.other_field in all_values and all_values
[self.other_field] == self.other_value and not value:
raise ValidationError(self.error_message, REQUIRED)
works both for forms and models with the proposed approach (all_values
is model_instance.__dict__.copy() in model field validation case).
Handling this specially for model instances would be really ugly:
def __call__(self, value, all_values={}, instance=None):
if instance is not None:
if hasattr(self.other_field, instance) and getattr
(self.other_field, instance) == self.other_value and not value:
raise ValidationError(self.error_message, REQUIRED)
elif self.other_field in all_values and all_values
[self.other_field] == self.other_value and not value:
raise ValidationError(self.error_message, REQUIRED)
and entirely unnecessary under the all_values approach.
Everybody is most welcome to prove me wrong :)
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