Back
Feb 18, 2010

Business logic in models

In my recent project there was a lot of data business logic, so I had to organize this code somehow. In this article I'll describe a few hints on how to it.

Mixins

Simple business logic functions should in models or managers. When there's a lot of them, the can be split in mixins.

# logic.py
class EventLogic(object):
    def start(self):
        if self.condition():
            # ...


# models.py
class Event(models.Model, EventLogic):
    name = models.CharField()
    # ...

Custom exceptions

For business logic errors you should declare custom exception classes. It's not fun to understand what this specific IntegrityError means.

Generic views

When all logic is in model and can throw, say, BusinessLogicException, we can write views like this:

from django.contrib import messages


def event_action(requets, event_id, action):
    # event = get_object_or_404(...)
    try:
        getattr(event, action)(request.user)
    except BusinessLogicException, e:
        messages.warning(request, e.message)

    return redirect(request.POST.get('next') or event)

Subscribe for the news and updates

More thoughts
Sep 8, 2023Technology
Smooth React virtual scroll with fixed rows/columns

One of our ongoing projects, Neptyne, introduces an Excel-like grid written in React. We used a library to apply virtual scroll to it, but we stumbled upon a problem with fixed rows and columns inside the grid. Here I would like to describe this problem, how it occurs, and how we handled it.

Sep 1, 2021TechnologyBusiness
Top 10 Web Development Frameworks in 2021 - 2022

We have reviewed the top web frameworks for server and client-side development and compared their pros and cons. Find out which one can be a great fit for your next project.

May 10, 2018Technology
How to Build a Cloud-Based Leads Management System for Universities

Lead management is an important part of the marketing strategy of every company of any size. Besides automating various business processes, privately-held organizations should consider implementing an IT solution that would help them manage their leads. So, how should you make a web-based leads management system for a University in order to significantly increase sales?

Jul 27, 2017Technology
How to Deploy Django app with AWS Elastic Beanstalk?

In this article I'll show you how to deploy Django application to AWS Beanstalk.

May 22, 2017Technology
Web Application Security: 10 Best Practices

Protection of WEB App is of paramount importance and it should be afforded the same level of security as the intellectual rights or private property. I'm going to cover how to protect your web app.

Mar 6, 2010Technology
Ajax form validation

There was a task to submit form with ajax, with server side validation of course. Obvious solution is to do validation and return json with erros. I didn't like idea of writing separate view for validation and then inserting errors in form html on client side. Especially since I already had a generic template for django form with errors display. In this article I'll describe how I solved the task.