Agfdhyk

My Model:

class Font(ValidateVersionOnSaveMixin, models.Model):

    id = models.UUIDField(primary_key=True, editable=True)  

    name = models.CharField(max_length=100, blank=False, null=False)





class Glyph(ValidateVersionOnSaveMixin, models.Model):

    id = models.UUIDField(primary_key=True, editable=True)  

    unit = models.CharField(max_length=100, blank=False, null=False, unique=True)

    font = models.ForeignKey(Font, on_delete=models.CASCADE)

I want to post the following JSON to add a Glyph to an already existing Font (having the fontId as ID) object.

{

  fontId: "4a14a055-3c8a-43ba-aab3-221b4244ac73"

  id: "40da7a83-a204-4319-9a04-b0a544bf4440"

  unit: "aaa"

}

As there is a mismatch between the ForeignKey Field font and the JSON propertyfontId I am adding source='font' in my Serializer:

class FontSerializer(serializers.ModelSerializer):

    class Meta:

        model = Font

        fields = ('id', 'name')





class GlyphSerializer(serializers.ModelSerializer):

    fontId = FontSerializer(source='font')

    class Meta:

        model = Glyph

        fields = ('id', 'unit', 'fontId' )

But the result is an BAD REQUEST Error:

{"fontId":{"non_field_errors":["Invalid data. Expected a dictionary, but got str."]}}

Update

The following Serializer gave me the result I was looking for.

class GlyphSerializer(serializers.ModelSerializer):

    fontId = serializers.PrimaryKeyRelatedField(

        queryset=Font.objects.all(),

        required=True,

        source='font',

        write_only=False

    )

    class Meta:

        model = Glyph

        fields = ('id', 'unit', 'version', 'fontId')

You have defined fontId as being a serialized object (FontSerializer). But that serializer in turn is defined as having both an id and a name. Where as your json dictionary is posting only an id. You would have to change that to a dictionary that contains both an id and a name

{

  fontId: {id: "4a14a055-3c8a-43ba-aab3-221b4244ac73",name: "some name" },

  id: "40da7a83-a204-4319-9a04-b0a544bf4440"

  unit: "aaa"

}

The reason you are getting this error is that during deserialization process, DRF calls .is_valid(raise_exception=True) before you can call serializer.save(validated_data). And non_field_errors lists any general validation errors during this process. In your GlyphSerializer, your FontSerializer is a nested serializer, which correlates to a Python dictionary. So it will raise an error like you encountered for any non-dictionary data types.

You could create a subclass of GlyphSerializer called GlyphCreateSerializer

class FontSerializer(serializers.ModelSerializer):

    class Meta:

        model = Font

        fields = ('id', 'name')





class GlyphSerializer(serializers.ModelSerializer):

    fontId = FontSerializer(source='font')

    class Meta:

        model = Glyph

        fields = ('id', 'unit', 'fontId' )



class GlyphCreateSerializer(GlyphSerializer):

    fontId = serializers.CharField()

And you can use GlyphCreateSerializer for the POST request on your Viewset.

You can user model_to_dict method as bellow:

from django.forms.models import model_to_dict

model_to_dict(obj)