How to validate post data if it exists with Django rest api

Question

I have a front end built with Angular 9 and a django rest api to capture the email for a subscription form.

I would to validate the entry from the frontend to make sure it does not exist in the database before it is saved if it does not exsit.

here is the model:

class Email(models.Model):
    email = models.EmailField(max_length=50)

    def __str__(self):
        return str(self.email)

The view set:

class EmailViewSet(viewsets.ModelViewSet):
    queryset = models.Email.objects.all() 
    serializer_class = serializers.EmailSerializer

    def create (self, request, *args, **kwargs):
        serializer = self.get_serializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        self.perform_create(serializer)
        return Response(serializer.data,status=status.HTTP_201_CREATED)

    def perform_create(self,serializer):
        queryset = models.Email.objects.filter(email=request.data)
        if queryset.exists():
            raise ValidationError('Email exist!')
        serializer.save(email=request.data)

willeM_ Van Onsem · Accepted Answer · 2023-10-11 10:10:36Z

3

You can simply mark the email field as unique=True ^[Django-doc]:

class Email(models.Model):
    email = models.EmailField(max_length=50, unique=True)

    def __str__(self):
        return self.email

The serializers in the Django REST framework take uniqness into acount and will check if an Email with the given email already exists. Furthermore the uniqness is also enforced at the database level, so normally if the database works properly it is impossible to create a second record with the same email value.

In the serializer you can specify the error message with:

from rest_framework import serializers

class EmailSerializer(ModelSerializer):
    email = serializers.EmailField(validators=[
        UniqueValidator(
            queryset=Email.objects.all(),
            message='Such email address already exists'
        )]
    )

    class Meta:
        model = Email
        fields = '__all__'

edited Oct 11, 2023 at 10:10

answered May 11, 2020 at 21:30

willeM_ Van Onsem

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2 Comments

namdi Over a year ago

Ok. thats nice and how would i return the error message on the angular front end for an end user @WillemVanOnsem

willeM_ Van Onsem Over a year ago

@namdi: you can specify the message in the serializer, see edit.

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