How can I implement custom validation in Django serializers?

How can I implement custom validation in Django serializers?

You can implement custom validation in Django serializers by overriding the validate method or using field-level validation.

Can you give me an example of field-level validation?

Sure! You can define a custom validation method for a specific field like this:

class MySerializer(serializers.Serializer):
    my_field = serializers.CharField()

    def validate_my_field(self, value):
        if not value.isalnum():
            raise serializers.ValidationError('This field must be alphanumeric.')
        return value

What if I want to validate multiple fields together?

In that case, you can override the validate method in your serializer:

class MySerializer(serializers.Serializer):
    field1 = serializers.CharField()
    field2 = serializers.CharField()

    def validate(self, attrs):
        if attrs['field1'] == attrs['field2']:
            raise serializers.ValidationError('Field1 and Field2 must not be the same.')
        return attrs