drf-service-layer 0.0.2

Simple package supports service-layered design for Django REST Framework.

DRF-Service-Layer

Simple package supports service-layered design for Django REST Framework.

Why service layer?

Have you ever wondered where to put your business logic when you use Django & DRF? There are several solutions with their pros and cons. Let's check them one by one.

1. Fat Models, Skinny Views
   This is one of the most popular ways to split business logic from views. To keep your views light, all the heavy codes go into "fat" models. But the problem is that as your project gets bigger, there are too many codes in your models. Besides, there are some cases when your business logic doesn't require any database access. They just exist in models because there aren't any places to be.

2. QuerySet/Managers
   It might be preferable to move your business logic from models to QuerySet or Managers. But still, this solution is not a good choice like the Fat Model approach if your business logic doesn't require any database access.

3. Forms or Serializers
   Probably the worst option. They each have their own purpose. Please don't do this.

4. Fat Views
   If all of your business logic stays in views, you'll have trouble understanding the flow of your views in a very short period of time. And if you inherit one of your fat views, the parent view and the child view are too strongly coupled. So you'll have a hard time extracting the legacy apis from your project.

5. Service layer
   Split your business logic into functions and put them in a separate layer ties models and views. To manage functions efficiently and improve the cohesion of codes, combine them into classes. In this way, views become easier to read and business logic becomes much more maintainable. Even though this may not be a standard design pattern from Django convention, some big companies like Doordash are already using this pattern by implementing it on their own.

How to use DRF-Service-Layer

Steps

1. install package

   pip install drf-service-layer
   

   💡 If you don't need to use any data when implementing business logic, skip step 2&3.

2. Decide a type of DTO.

   💁 What is DTO?
   DTO(Data Transfer Object) is an object that carries data between processes.
   In DRF-Service-Layer, DTO is an object used for transferring data necessary for your business logic.

   DTO works between views and the service layer. If you want to transfer any data from a view to a service, implement create_dto() in your view that inherits GenericAPIView from DRF-Service-Layer. We'll cover this shortly.

   • DTO as dataclass

     # services.py
     from dataclasses import dataclass
     from typing import Union
     
     
     @dataclass
     class OrderDTO:
         user_id: int
         sort: Union[str, None]
         is_paid: bool
     

   • DTO as dictionary

   • DTO as list

   • or any type you want...

3. Implement create_dto() in views.

   If you decide to use dataclass as DTO:

   # views.py
   from drf_service_layer.views import GenericServiceAPIView
   
   
   class OrderAPIView(GenericServiceAPIView):
   
       def create_dto(self, request) -> OrderDTO:
           order_id = self.kwargs['order_id']
           order = get_object_or_404(Order, pk=order_id)
   
           return OrderDTO(
               user_id=self.request.user.id,
               sort=self.request.query_params.get("sort"),
               is_paid=order.is_paid
           )   
   

4. Create a service class and implement business logic in it.

   # services.py
   from drf_service_layer.services import Service
   
   
   class OrderService(Service):
   
       def any_business_function(self):
           user_id = self.dto.user_id
           sort = self.dto.sort
           is_paid = self.dto.is_paid
           # business logic goes here. 
   

5. Specify a service class into a view as service_class.

   # views.py
   class OrderAPIView(GenericServiceAPIView):
       service_class = OrderService  # new
   
       def create_dto(self, request) -> OrderDTO:
           # ...
   

6. Use service layer in a view.

   # views.py
   class OrderAPIView(GenericServiceAPIView):
       service_class = OrderService
   
       def create_dto(self, request) -> OrderDTO:
           # ...
   
       def get(self, request, *args, **kwargs):  # new
           # ...
           self.service.any_business_function()
           # ...
           return Response(...)
   

Description

When a view is initialized by DRF's initial() method, create_dto() you have implemented is called. The return value of create_dto() is set to self.dto and used as an argument when instantiating the service layer. DTO is already injected into the service layer as an instance variable(self.dto), so you don't need to care about parameters when implementing business logic and using them. After all, you can call any function from the service layer using self.service in your views.

Inspired by

• How to implement a service layer in Django + Rest Framework