Separation of Business Logic and Data Access in Django

In our Django views, there are two distinct and significant concerns: how we carry out database actions and how we implement business logic in our endpoints. Simple read, create, update, and delete operations similar to those offered by Django's Model layer may or may not be involved in the former. In the data management layer, decisions are made about how to carry out these CRUD operations and which particular operations to carry out in a single atomic transaction.

A clean architecture is essential for modern web applications' scalability, maintainability, and efficiency. This architecture's division of business logic and data access is one of its main features. As a high-level web framework, Django urges developers to follow this guideline to create reliable applications. This essay will define business logic and data access, explain why it's crucial to keep them apart, and show us how to use Django to accomplish this.

A decent project structure for a medium-sized project can be like this. Where we would handle validations in the forms.py file and our utility functions would live in the services.py file.

my_project/
├── my_app/
│  ├── __init__.py
|    ├── admin.py
|    ├── forms.py
│  ├── models.py
|   ├── services.py
│   ├─ urls.py
│   ├─ views.py

├──my_project/
│   ├── __init__.py
│   ├── asgi.py
│   ├─ settings.py
│   ├─ urls.py
│   ├── wsgi.py
├── manage.py

Understanding the Data Access in Django

Modern online applications, especially those developed with Django, need to grasp the difference and link between data access to create effective, maintainable, and scalable systems.

Data Access

The techniques and technologies used to communicate with data storage systems, especially databases, are collectively referred to as data access. The following Django components are generally used to handle data access:

1. Migrations: Django uses migrations to handle schema changes to the database over time. They give programmers the ability to create, edit, and remove database tables in an organized manner.

• Version control over database schema modifications is made possible by migrations, which facilitates developer collaboration and allows for the easy rollback of changes as needed.
• Migrations lessen the possibility of problems brought on by schema incompatibilities by ensuring that the database schema is constant throughout various contexts .

2. Models: Python classes called models determine the organization of your data. Every model maps to a database table, where the fields are represented by class attributes.

• An interface for carrying out CRUD (Create, Read, Update, Delete) tasks is provided by models. They capture the behaviors connected to the data as well as the data structure.
• Model-driven development streamlines database interactions by allowing developers to concentrate on higher-level application logic. Django automatically produces the required SQL queries for common tasks.

3. QuerySets: Django offers QuerySets, which are sets of database queries for data retrieval and manipulation.

• QuerySets allow for lazy evaluation, which means that queries are only run when specifically required. Better performance and more economical use of resources may result from this.

Understanding Business Logic

Business Logic:

The procedures and guidelines that control the creation, processing, and manipulation of data inside an application are referred to as business logic. It functions as the foundation for the functionality of the program, including essential elements like:

1. Making Decisions defining parameters that control the application's behavior in response to user input. For example, based on income and credit score, deciding whether to approve a loan application.

2. Compiling putting in place fundamental features like workflows and computations. This can entail computing total expenses and applying discounts in an e-commerce platform.

3. Validation ensuring that information satisfies certain requirements before processing or storing. For instance, verifying upon registration that a user's email address is distinct.

Decoupling Business Logic and Data Access in Django

In order to successfully decouple Django's data access from business logic, take into account these recommended practices:

• In our Django Application - We can create create a services.py file or a services folder with __init__.py file and Python files to handle business logics.
• For Data Manipulation and Creation - We can handle logics in the forms.py or serializers.py files and other option would be create db_utils.py files and related logics in this file.

1. Using Services.py and Service Classes

Put business logic into service classes that manage particular tasks, and keep views concentrated on responding to HTTP requests.

services.py

from .models import User

class UserEmailService:
  
  	@staticmethod
    def send_email(self, email):
        if not self.validate_email(email):
            raise ValueError("Invalid email")
        try:
          	# We can send email here
            return True
        execpt:
          	# Log the error
            return False
          
  	@staticmethod
    def validate_email(self, email):
        return "@" in email

2. Leverage Django Forms

To validate and process input while keeping views clear and user-interactive-focused, utilize Django forms.

froms.py

from django import forms
from .models import User

class UserForm(forms.ModelForm):
    class Meta:
        model = User
        fields = ['username', 'email']

    def clean_email(self):
        email = self.cleaned_data.get('email')
        if User.objects.filter(email=email).exists():
            raise forms.ValidationError("Email already in use.")
        return email
      
   	def save(self, *args, **kwargs):
      	user = super.save(*args, **kwargs)
        user.is_active = False
        user.save()

3. Keep Views Lean

Views should handle requests and responses in the main, leaving service classes and models to handle more complicated logic.

views.py

from django.shortcuts import render, redirect
from .forms import UserForm
from .services import UserService

def create_user_view(request):
    if request.method == 'POST':
        form = UserForm(request.POST)
        if form.is_valid():
            user = form.save()
            UserService.send_email(user.email)
            return redirect('success_url')
    else:
        form = UserForm()
    return render(request, 'create_user.html', {'form': form})

Related Links

• Django Basics
• Django - MVT Architecture
• Function Based Views in Django
• Class Based Views in Django
• Python | User groups with Custom permissions in Django

Conclusion

To build a robust Django application, it’s important to understand the difference between data access and business logic. Developers can build efficient applications to accurately monitor and demonstrate business logic through validation, processing, and decision making using Django’s robust ORM. This strategic approach results in more efficient and scalable implementation by improving the user experience and improving the quality of the code overall.

Why are Django's business logic and data access sections kept apart?

It enhances maintainability, scalability, and clarity in the codebase.

In what ways do Django forms aid in the division of labor?

They handle input validation and processing, ensuring views remain clean and organized.

Why is maintaining a lean viewpoint important?

Lean views improve readability and maintainability by delegating complex logic to service classes and models.

How can I make sure that business logic is correct?

To ensure that business logic operates correctly regardless of data access, implement unit tests.