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
Nov 27, 2024Technology
Stoicism At Work

This article explores how Stoic principles can be applied in the workplace to navigate stress, improve self-control, and focus on what truly matters, with practical examples from the author’s experience in software development.

May 12, 2022Technology
Increasing performance by using proper query structure

Earlier in our previous article "Improve efficiency of your SELECT queries" we discussed ways to profile and optimize the performance of SELECT queries. However, to write complex yet efficient SQL queries, there is a thing to remember about.

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.

Feb 28, 2017Technology
How to write an API in Django

There is such a term as Remote Procedure Call (RPC). In other words, by using this technology, programs can call functions on remote computers. There are many ways to implement RPC.

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.

Mar 4, 2011Technology
Css sprite generation

I've created this small sprite to create css sprites. It glues images from directory directory into single file and generates corresponding css.