Question

I want to be able to do:

def update_profile(request, username):
    user = Profile.objects.get(user__username=username)

    # update subset of profile, eg value_to_company is set in request.POST
    # but user (or an arbitrary number of other attributes) is not
    profile = ProfileForm(request.POST, instance=user)

    if not profile.is_valid():
        print profile.errors  #user is required

The problem that I have with this is that user definitely exists and is part of the instance, and I can’t find anything in the docs to suggest that instance data wouldn’t get into the bound data. But I also can’t find anything that explicitly says that it will.

(The rest of this is justification for why I’m doing things the way I am, and ideas for solutions, you probably don’t need to read it.)

If you want to know why I’m going through a form–not essential to the question–it’s because I’ve got something like this:

class Profile(models.Model):
    user = models.ForeignKey(auth.models.User)
    value_to_company = models.IntegerField()

class ValueField(forms.Field):
    def to_python(self, value):
        vals = {'high': 0,
                'mid': 1}
        return vals[value]

class ProfileForm(forms.ModelForm):
    value_to_company = ValueField()

    class Meta:
        model = Profile

That is, I’m doing type api-to-internal-representation-coercion in my forms already and I’d like to continue using that.

I could reimplement the forms.is_valid() loop, just checking for the fields on the form that already exist, something hacky like:

# replaces `if not profile.is_valid()` above:
errors = []
for field in request.POST.iterkeys():
    if field in profile.fields:
        profile.fields[field].to_python()
        if not profile.fields['field'].clean():
            errors.append #something

(I haven’t actually looked at the logic internal logic, so I know that’s wrong, but you get the idea.)

Answer 1

You likely just need to add exclude = ('user',) to your form. The forms instance mostly determines initial values, if your form includes the user field, but that field is posted with a blank value it will try to blank out the user field, resulting in the error.