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
Apr 3, 2024Technology
Test Analysis at the Product Level

Test analysis is an essential and crucial activity in the testing process. A well-organized test analysis provides an adequate level of confidence in the overall effectiveness of the testing and contributes to the delivery of high-quality software.

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.

Jan 28, 2017Technology
Creating a site preview like in slack (using aiohttp)

In this article we will write a small library for pulling metadata and creating a preview for a site just like Slack does.

Jan 9, 2017Technology
How to Use GraphQL with Django

GraphQL is a very powerful library, which is not difficult to understand. GraphQL will help to write simple and clear REST API to suit every taste and meet any requirements.

Oct 22, 2016Technology
Solr Sharding

When dealing with one of our projects (LookSMI media monitoring platform) we have to handle the huge volume of data – and its quantity is constantly growing. At the same time, we must run quick searches with smart rules. In this article I'll explain how we have achieved required performance.

Sep 22, 2016Technology
Angular Form Validation

In this article, we will describe some useful scripts and directives we use with angular form validation in our projects.