Django field not appearing in validated data but it's in request

Question

I have these serializers:

class OneSerializer(serializers.ModelSerializer):
    class Meta:
        model = OneModel
        fields = ['time_column', 'event_column']


class TwoSerializer(serializers.ModelSerializer):
    survival_columns = OneSerializer(many=True, required=False)
    
    class Meta:
        model = UserFile
        fields = ['id', 'name', 'survival_columns']

Now in the create method I'm trying to retrieve survival_columns values from validated_data but it's not present! If I print the POST data the field and values appear correctly:

def create(self, validated_data):
   print(self.context['request'].POST)  # <QueryDict: {'name': ['Datos Clinicos de prueba.csv'], 'survival_columns': ['{"event_column":"Prueba","time_column":"prueba"}']}>
   print(validated_data)  #  {'name': 'Datos Clinicos de prueba.csv'}

Why is the field survival_columns being filtered from the request?

Answer 1

I was making the request with FormData and the survival_columns field was an array which was Stringyfied before being sent. This combination of FormData and JSON is nos supported by Django REST Framework as this article pointed out.

The solution was manually decode the field using json built-in package:

def create(self, validated_data):
    ...
    survival_columns_str = self.context['request'].POST.get('survival_columns', '[]')
    survival_columns = json.loads(survival_columns_str)
    ...