Django Rest Framework Tips and Tricks

Original Post in https://skamalakannan.dev/posts/django-rest-framework-tips/

Django Rest Framework is a powerful tool for creating API, and it comes with a lot of features. Here is the list of tips that will help in developing your API better.

Sending common field in all the responses

We might have use cases where we want to send a lot in all our responses, like resource URI, create date, or created user kind of fields.We can use serializer mixins for this purpose. Mixins are abstract classes, and we can define all the variables in these mixins, and we can inherit these mixins to the actual class.

from user.serializers import UserMinimumSerializer

class CreatedModifiedSerializer(serializers.Serializer):
    created_date = serializers.DateTimeField(read_only=True)
    created_by = UserMinimumSerializer(read_only=True)
    modified_date = serializers.DateTimeField(read_only=True)
    modified_by = UserMinimumSerializer(read_only=True)

    class Meta:
        abstract = True

class OrderSerializer(CreatedModifiedSerializer):

    class Meta:
        model = Order
        fields = '__all__'

In the above example, we have created a CreatedModifiedSerializer as a mixin. It will get applied to the OrderSerializer, if the Order doesn't have any one of the fields declared in the mixin, we will receive an exception.

Return computed value from the model

if you have a scenario is to send the computed value. We can create a property for a model and specify the property name directly in the Serializer class.

class Order(models.Model):
    qty = models.IntegerField()
    price_per_qty = models.DecimalField(max_digits=5, decimal_places=2, default=0.0)

    @property 
    def total_amount(self):
        return self.qty * self.price_per_qty

class OrderSerializer(models.ModelSerializer):

    class Meta:
        model = Order
        fields = ('qty', 'price_pert_qty', 'total_amount') #Total amount is property of the model

Since the total_amount is a property, it will pick it directly. We can also declare the field type, specify as read-only, or result in an AttributeError exception.

Saving nested serializer

If we want to create or update a nested model relation. drf-writable-nested is a package that comes for rescue; it supports nested serializer both create and update operations. it also available supports for OneToOne, ForeignKey, ManyToMany.
https://github.com/beda-software/drf-writable-nested

from drf_writable_nested.serializers import WritableNestedModelSerializer
from rest_framework.serializers import ModelSerializer

class OrderItemSerializer(ModelSerializer):
    class Meta:
        model = OrderItems
        fields = '__all__'

class OrderSerializer(WritableNestedModelSerializer):
    items = OrderItemSerializer(many=True)

    class Meta:
        model = Order
        fields = '__all__'

Accept object id while create and update, return object through serializer

By default, DRF accepts and returns the field in the same format. If the use case is to accept the id update and create but return the serialized object. We can use PresentablePrimaryKeyRelatedField from the drf-extra-fields package for this purpose.
The custom field takes two arguments one is the queryset of the model, and another one presentation_serializer is a serializer class for the model.

from drf_extra_fields.relations import PresentablePrimaryKeyRelatedField
from rest_framework.serializers import ModelSerializer

class OrderSerializer(ModelSerializer):
    items = OrderItemSerializer(many=True)
    order_type = PresentablePrimaryKeyRelatedField(
        queryset = OrderType.objects.all(),
        presentation_serializer=OrderTypeSerializer
    )
    class Meta:
        model = Order
        fields = '__all__'