Validating input in custom manager methods?

Question

Let's say I'm creating a polls app, and I want users to create their polls and their choices together, and not modify them at a later point.

At the moment I have something like:

class PollManager(models.Manager):
    def create_poll(self, name, owner, choices):
        new_poll = Poll(name=name, owner=owner)
        new_poll.save()
        for name in choices:
            Choice(name=choice, poll=new_poll).save()

class Poll(models.Model):
    name = models.CharField(max_length=30)
    objects = PollManager()

class Choice(models.Model):
    name = models.CharField(max_length=30)
    poll = models.ForeignKey(Poll)

However, if the input to the Poll.objects.create_poll method isn't valid, I might end up accidentally saving a poll without any choices, for example. But I don't think I can leave new_poll.save() until the end without getting errors when creating the Choice instances.

I can put some try...except stuff at the start of the create_poll method to make sure the input is all valid, but I'm concerned I'll be breaking DRY if I do this.

Should I be using a custom manager method in this way? If so, how should I best deal with validation? If not, what's considered to be good practice for some equivalent functionality?

Thanks in advance.

score 0 · Answer 1 · answered Apr 08 '14 at 04:02

0

I would validate data in the form clean/save methods (if you use django forms).

answered Apr 08 '14 at 04:02

Bigcortex

145
5

Thanks. I think I might have been taking the heavy models thing a bit too far. – somnicule Apr 08 '14 at 04:09

score 0 · Answer 2 · answered Apr 08 '14 at 09:41

0

You can use django model forms which vadilates fields according to your model link

answered Apr 08 '14 at 09:41

user3336706

1
3

Right, but I'd be creating multiple models from one form in this case. – somnicule Apr 08 '14 at 21:31

Validating input in custom manager methods?

2 Answers2