Django Rest Framework - Get related model field in serializer

Question

I'm trying to return a HttpResponse from Django Rest Framework including data from 2 linked models. The models are:

class Wine(models.Model):

    color = models.CharField(max_length=100, blank=True)
    country = models.CharField(max_length=100, blank=True)
    region = models.CharField(max_length=100, blank=True)
    appellation = models.CharField(max_length=100, blank=True)

class Bottle(models.Model):

    wine = models.ForeignKey(Wine, null=False)
    user = models.ForeignKey(User, null=False, related_name='bottles')

I'd like to have a serializer for the Bottle model which includes information from the related Wine.

I tried:

class BottleSerializer(serializers.HyperlinkedModelSerializer):
    wine = serializers.RelatedField(source='wine')

    class Meta:
        model = Bottle
        fields = ('url', 'wine.color', 'wine.country', 'user', 'date_rated', 'rating', 'comment', 'get_more')

which doesn't work.

Any ideas how I could do that?

Thanks :)

Solution 1

Simple as that, adding the WineSerializer as a field solved it.

class BottleSerializer(serializers.HyperlinkedModelSerializer):
    wine = WineSerializer(source='wine')

    class Meta:
        model = Bottle
        fields = ('url', 'wine', 'user', 'date_rated', 'rating', 'comment', 'get_more')

with:

class WineSerializer(serializers.HyperlinkedModelSerializer):

    class Meta:
        model = Wine
        fields = ('id', 'url', 'color', 'country', 'region', 'appellation')

Thanks for the help @mariodev :)

Solution 2

If you want to get specific field you can use Serializer Fields

https://www.django-rest-framework.org/api-guide/fields/

    class BottleSerializer(serializers.HyperlinkedModelSerializer):
        winecolor = serializers.CharField(read_only=True, source="wine.color")

        class Meta:
            model = Bottle
            fields = ('url', 'winecolor', 'user', 'date_rated', 'rating', 'comment', 'get_more')

Comments

[mariodev]

Glad you sort that out. Can you also please explain what WineSerializer class stands for, so we have a clear answer..

[arturataide]

I've done this but I'm getting the fallowing error HyperlinkedRelatedField requires the request in the serializer context. Add context={'request': request} when instantiating the serializer.`. What am I doing wrong?

[Mahabubur Rahaman Melon]

got error like this: AssertionError(u"HyperlinkedIdentityField requires the request in the serializer context. Add context={'request': request} when instantiating the serializer.",) is not JSON serializable.

[shanemgrey]

You shouldn't need the source='wine' argument since it's the same as the name. In fact I'm surprised if you aren't getting a runtime error for that. Instead you can add other args like (many=False, read_only=True)

[roboslone]

To anybody with the same problem - you don't have to use HyperlinkedModelSerializer, ModelSerializer will do just fine.

[mgalgs]

This will result in an embedded object under the wine property. Is there a way to get specific fields from the related Wine model embedded directly in the top-level object?

[Rishi Latchmepersad]

For anyone else who spent way too long trying to figure out how this links to the related serializer, the source="wine.color" follows the foreign key relationship defined in the model. In this case, the foreign key was named 'wine', and the related field is 'color'.