Django: Rest Framework (Serializer)

I'm new to using the django rest framework.

I'm trying to understand how I can validate a field with the serializer based on the input from the user, for example:

Serializer:

from rest_framework import serializers

VALID_REGION = 'region'

def validate_region(value):
    
    if value != VALID_REGION:
        raise serializers.ValidationError('Invalid region, make sure region parameter is spelled correctly.')
    
    return value

class RegionSerializer(serializers.Serializer):
    region = serializers.CharField(required=False, validators=[validate_region])

Here I want to validate that the region is spelled correctly.

views.py

 def get(request, *args, **kwargs):

        serializer = RegionSerializer(data = request.data)

        if serializer.is_valid():
            
            data = serializer.validated_data

            region   = data.get('region', '')

            regions = region_lib.get_regions(region)

            return Response({"regions" : regions}, status=status.HTTP_200_OK)

        else:
            errors = serializer.errors

            return Response({"error" : errors}, status=status.HTTP_400_BAD_REQUEST)

Here I pass 'regoin' misspelling it intentionally.

{
    "regoin": "Test"
}

When I run serializer.is_valid() it returns true.

Not sure what I'm missing.

You should modify your request method from GET to POST. For example, change the following code:

From:

def get(request, *args, **kwargs):

To

def post(request, *args, **kwargs):

By using def get(request, *args, **kwargs):, your endpoint only allows GET requests. As a result, you cannot send a request body, and self.request.data will be {}. Additionally, in your RegionSerializer, you have set the region field to be optional with required=False:

region = serializers.CharField(required=False, validators=[validate_region])

This explains why serializer.is_valid() in your views always returns True.

When you change from def get(request, *args, **kwargs): (GET) to def post(request, *args, **kwargs): (POST), and you pass your request body as follows:

{"region": "region"}

This will pass the serializer.is_valid() check.

However, if you pass {"region": "Region"}, it will not cause serializer.is_valid() to return False.

Note: If your request body is empty, serializer.is_valid() will also return True since the region field is optional.

n your code, the misspelled field 'regoin' is being considered as a valid field because the RegionSerializer has required=False for the 'region' field. This means that the field is not required and can be omitted from the data. When you pass 'regoin' instead of 'region', it is ignored because it doesn't match any defined fields and doesn't raise a validation error.

To ensure that the misspelled field raises a validation error, you can remove required=False from the 'region' field in the RegionSerializer. This way, the field will be required, and any misspelled or missing 'region' field will trigger a validation error.

class RegionSerializer(serializers.Serializer):
    region = serializers.CharField(validators=[validate_region])