Django REST Framework serializer field required=false

Question

from the documentation:

read_only
Set this to True to ensure that the field is used when serializing a representation, but is not used when updating an instance during deserialization.

Defaults to False

required
Normally an error will be raised if a field is not supplied during deserialization. Set to false if this field is not required to be present during deserialization.

Defaults to True.

So I have a model which has a field that’s not nullable but I want it to be populated in the pre_save method, so I have set the field to required=False in serializer, but doesn’t seem to work. I am still getting error when saving the record.

class FavoriteListSerializer(serializers.ModelSerializer):
    owner = serializers.IntegerField(required=False)
    class Meta:
        model = models.FavoriteList

Update:
I have added serializer_class = serializers.FavoriteListSerializer to the ViewSet, now instead of getting This field is required, which I think got past the validation but then I am getting This field cannot be null. I have checked the pre_save method is not being executed, any ideas?

Asked By: James Lin

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Answer 1

Yeah, I ran into this issue at some point as well. You need to also update the validation exclusions.

class FavoriteListSerializer(serializers.ModelSerializer):
    owner = serializers.IntegerField(required=False)
    class Meta:
        model = models.FavoriteList

    def get_validation_exclusions(self):
        exclusions = super(FavoriteListSerializer, self).get_validation_exclusions()
        return exclusions + ['owner']

Answered By: Kevin Stone

Answer 2

Late Entry to this thread. This issue was fixed in django-rest-framework 2.3.13. Here is the link of the PR.

You use it like this in your case:

    class Meta:
        model = models.FavoriteList
        optional_fields = ['owner', ]

Answered By: Pankaj Singhal

Answer 3

In case somebody lands here with a similar issue, pay attention to the following attributes along with required:

allow_blank:

If set to True then the empty string should be considered a valid value.

allow_null:

Normally an error will be raised if None is passed to a serializer field.

required:

Normally an error will be raised if a field is not supplied during deserialization.

I was straggling to figure out why I was getting a validation error with required=False where I had missed the allow_null attribute.

Answered By: Wtower

Answer 4

If you have unique_together constraint on one of the fields you are trying to set required=False you need to set validators=[] in serializers Meta like

class FavoriteListSerializer(serializers.ModelSerializer):
    owner = serializers.IntegerField(required=False)
    class Meta:
        model = models.FavoriteList
        validators = []

Here is the original answer

Answered By: Vaghinak

Answer 5

You can also do this:

class ASerializer(serializers.HyperlinkedModelSerializer): 
    owner = serializers.HiddenField(default=serializers.CurrentUserDefault())

    ...

As referred here: https://www.django-rest-framework.org/api-guide/validators/#advanced-field-defaults
There you can also find the case when you also wanna let the view show owner

Answered By: Michele

Answer 6

In 2020, for DRF 3.12.x, the approach that I prefer the approach that relies on
Serializer’s extra_kwargs.

So assuming your

class FavoriteListSerializer(serializers.ModelSerializer):
    owner = serializers.IntegerField(required=False)
    class Meta:
        model = models.FavoriteList
        fields = ["owner"]  # and whatever other fields you want to expose
        extra_kwargs = {"owner": {"required": False, "allow_null": True}}

Answered By: Illya Gerasymchuk

Django REST Framework serializer field required=false

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