Add additional data to the model data returned by a Django serializer

Question

I am using the Django REST framework to create an API. I would like to add data from more than one model to the serialised output.

At the moment my serialiser looks like this:

class ItemSerializer(serializers.HyperlinkedModelSerializer):
    class Meta:
        model = Item
        fields = ('url', 'owner', 'item_type')

I would like to add an

item_cost

value from my Costs model to the serialised output (a different cost for each item in the Item model). I would also like to add a unix timestamp value to the serialised output (one value to be placed at the end of all of the other serialised output).

My serialiser is used in a view as follows:

class ItemViewSet(viewsets.ModelViewSet):
    queryset = Item.objects.all().order_by('-date_added')
    serializer_class = ItemSerializer

I can't work out how to add the other data items to the serialised output.

Gustavo Carvalho · Accepted Answer · 2016-03-28 12:22:13Z

2

You can use a SerializerMethodField from rest_framework.serializers and create a method that returns the value you are looking for, eg:

class ItemSerializer(serializers.HyperlinkedModelSerializer):
    cost = serializers.SerializerMethodField()

    def get_cost(self, obj):
        value = ... # calculate your value
        return value

    class Meta:
        model = Item
        fields = ('url', 'owner', 'item_type', 'cost')

Reference in the docs: http://www.django-rest-framework.org/api-guide/fields/#serializermethodfield

answered Mar 28, 2016 at 12:22

Gustavo Carvalho

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2 Comments

Bill Noble Over a year ago

That is perfect Gustavo! Is there a way to access the query params from the calling url in the get_cost function so I can do an action that depends on the query?

Gustavo Carvalho Over a year ago

Yes you can. From inside the method, you can access the QueryDict: self.context.get('request').query_params

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