Django Rest Framework Business Logic

Question

I am trying to create a backend with Django Rest Framework and am trying to determine where to place the business logic. Would it go in the views.py? I would like to create more complex services than just getting a list of objects or grabbing one specific object. Any guidance would be appreciated, thanks. I realize there is a discussion about the business logic in a generic Django project but I am asking specifically about the django rest framework.

Answer 1

It is more about design patterns rather than Django Rest Framework.

Here are some tips:

• Providing interfaces using REST should not involve any specific code related to data manipulation or business logic.
• Using an MVC approach does not mean that you shouldn't layer your application.
• You should be able to test your business logic without touching the UI at all.
• Some people may suggest putting business logic in models. But I do not agree with them, since Django models are different from domain models and business related tasks such as tax calculation.
• Before getting stuck in MVC, You could read more about The MVC implemented in MVC three-tier architecture
• I suggest having a business layer and related apps putting your business logic there.

Suppose that you have an online coffee shop & you'd like to provide a REST API for ordering coffees.

Here are my suggested code samples:

myapp/views.py:

    def order(request, quantity=1):
        # Process the order by calling the mapped method
        order_id = CoffeeShopService.place_order(quantity)
        return HttpResponse({'order_id': order_id, mimetype='application/json')

myapp/services.py:

    class CoffeeShopService(object):
        @staticmethod
        def place_order(quantity):
           # do the business logic here
           return order_id

Answer 2

It is a design patterns Questing in Rest Framework, I guess. Here is a Detailed Overview of how i use Layered Approach in my API build on Rest Framework!

It is a little more layered for the sake of Easy Maintenance and utilizes Design Patterns and GRASP Principal most importantly!

Layered Approach Package Level View

Further Classification:

Now an Example of How I go through Layers:

1. A Request is made to example.com/Customer/profile @project/urls.py

2. The Request is forwarded to the Respective URL's Layer (@app/urls/Customer_Url)

3. URL's Pass it to the Respective Viewset (@app/Viewsets/Customer_Viewsets/Customer_Signup.py)

4. It being a Post Request, (I assume for this Example) is Forwarded to Business Logic Layer (@app/BusinessLogicLayer/BLL.py)

5. The Business Logic Layer has an Abstract Implementation(Act as Interface of IBLL) and it forwards the request to respective method to check for all my Business Rules! (@app/BusinessLogicLayer/SUB_BLL/Customer/*)

6. The Request is then Forwarded to the Data Access Layer which stores the Data of User in Database. and So forth! (@app/DataAccessLayer/DAL.py)

Answer 3

maybe this is a slightly eccentric way, but I think it's quite helpful to wrap the logic into the serializer by adding methods in it.

For example

serializer:

class OrderSerializer(serializers.ModelSerializer):
    class Meta:
        model = Order
        fields = (
            'id',
            'total',
            'discount',
        )

    def calculate_discount(self, whatever_params):
        # calculate discount if you need... and return it

    def calculate_tax(self, whatever_params):
        # calculate tax amount if you need...and return it

    def calculate_grand_total(self, whatever_params):
        # calculate grand total if you need and return it

    def create(self, validated_data):
        # You can make an order by applying 
        # some logic in the calculation method.
        # Maybe by adding a bit of the context 
        # you sent as parameters from view.