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
Aug 27, 2024Technology
An Effective Preparation Algorithm for ISTQB Certification

This article offers key insights into the ISTQB certification and shares a proven preparation strategy to help candidates succeed.

Aug 27, 2020Technology
5 tips for designing database architecture

Designing database architecture is a challenging task, and it gets even more difficult when your app keeps getting bigger. Here are several tips on how to manage your data structure in a more efficient way.

Feb 12, 2020Technology
5 Best Payment Gateways For 2020

We reviewed the best payment gateways in 2020. Here’s our comparison of their features, advantages, and disadvantages.

May 26, 2017Technology
Tutorial: Django User Registration and Authentication

In this beginners friends article I'll explain how to make authentication with Google account on your Django site and how to make authentication for you REST API.

Mar 2, 2017Technology
API versioning with django rest framework?

We often handling API server updates including backwards-incompatible changes when upgrading web applications. At the same time we update the client part, therefore, we did not experience any particular difficulties.

Feb 18, 2010Technology
Absolute urls in models

Everybody knows about permalink, but it's usually used only in get_absolute_url. I prefer to use it for all related model urls.class Event(models.Model):# ...@models.permalinkdef edit_url(self):return ('event_edit', (self.pk, ))And then in template:<a href="{{ event.edit_url }}">Редактировать событие</a>