问题
In suppliment to this question, if business logic should be in the model, how do I return an error message from the model?
def save(self, *args, **kwargs):
if <some condition>:
#return some error message to the view or template
回答1:
Pastylegs is correct, but you shouldn't be doing that sort of logic in the save method. Django has a built-in system for validating model instances before saving - you should use this, and raise ValidationError where necessary.
回答2:
Raising an exception is the way to report a program logic error (an error in 'business logic'), which is what you are talking about. You can just raise an Exception, as pastylegs proposes (be aware that SomeException is just a placeholder):
from django.core.exceptions import SomeException
def save(self, *args, **kwargs):
if <some condition>:
raise SomeException('your message here')
You can find the available exceptions fpr django here: https://docs.djangoproject.com/en/1.3/ref/exceptions/ ,plus you can also use the standard python exceptions, for which you can find documentation here: http://docs.python.org/library/exceptions.html
I would recommend you to find an Exception that describes your problem, or you will be pretty confused if that error shows up in a few weeks, when you cannot remember what exactly you have been doing now.
来源：https://stackoverflow.com/questions/9531850/how-to-return-an-error-message-from-the-model