Using models clean method for fields validation

Question

I need to check the model field for a list of available items before I save them to the database.

models.py

class Vendors(models.Model):
    COUNTRY_CHOICES = tuple(countries)
    ...
    country = models.CharField(max_length=45, choices=COUNTRY_CHOICES)
    ...

class for saving models

class CsvToDatabase(APIView):

    def post(self, request, format=None):
        data = request.data
        for key, vendor in data.items():
            Vendors(
                ...,
                country=vendor['Country'],
                ...,

            ).save()

        return Response({'received data': request.data,
                         'message': 'Vendors from vendors_list were successfully added to the database'})

For validation Im added clean method to models

def clean(self):
    if self.country not in [x[1] for x in countries]:
        raise ValidationError(detail="Country name does not match to the country list ")

But it doesnt work

Next step I added the same code to method save

def save(self):
    if self.country not in [x[1] for x in countries]:
        raise ValidationError(detail="Country name does not match to the country list ")

And it works, but I read that using validation in the save method is not correct. And the correct method for use - clean, why in my case it does not work?

The correct way is indeed to use clean(), however the clean() method on a model isn't called automatically. It gets called when you clean a ModelForm for the model (by checking form.is_valid()) or when you validate a ModelSerializer. You can also just call it yourself. Create the Vendors object, call full_clean() first (and catch the ValidationError) and only after that call save(). Note: if you call full_clean(), the model will already validate that the country is set correctly, you don't need to add that in clean(). — dirkgroten
– dirkgroten, Commented Feb 19, 2020 at 12:39

dirkgroten · Accepted Answer · 2020-02-19 12:44:53Z

1

See model validation for a full explanation of how validating models works.

In short: To validate an object, you need to call full_clean() on the object. This does not happen automatically! It happens when:

You use a ModelForm and call is_valid() on the form
You use a ModelSerializer in DRF and call is_valid() on the serializer
You call full_clean() explicitly

In your case, just create the object, call full_clean() and then save(). Note you don't even have to add your own check (clean() method) because the check for valid choices is automatically performed by Django during clean_fields() when choices is set on a field:

v = Vendors(country=vendor['country'], ...)
try:
    v.full_clean()
except ValidationError as e:
    # do something e.g. return error response
v.save()
return Response(...)

answered Feb 19, 2020 at 12:44

dirkgroten

20.8k2 gold badges32 silver badges46 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Jekson Over a year ago

Great, it works and it's very useful information for me. One more thing for me - how to catch the exceptions ? Now I have an exception from the clean model method, and I would like to use an exception from the POST class method. Im created a new question for this. I'd appreciate your help.

Ramon K. Over a year ago

Notice: ModelSerializer.is_valid doesn't actually call Model.full_clean

Collectives™ on Stack Overflow

Using models clean method for fields validation

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related