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
One of the key requirements for modern UI is being performant. No matter how beautiful your app looks and what killer features it offers, it will frustrate your users if it clangs.
Django ORM is a very abstract and flexible API. But if you do not know exactly how it works, you will likely end up with slow and heavy views, if you have not already. So, this article provides practical solutions to N+1 and high loading time issues. For clarity, I will create a simple view that demonstrates common ORM query problems and shows frequently used practices.
Welcome all who are reading this article. I was given a task of creating a parser (spider) with the Scrapy library and parsing FTP server with data. The parser had to find lists of files on the server and handle each file separately depending on the requirement to the parser.
In this article, we will describe some useful scripts and directives we use with angular form validation in our projects.
I've created this small sprite to create css sprites. It glues images from directory directory into single file and generates corresponding css.
In UNIX way, each view should solve single task. This is good idea, but sometimes we need to mix logic of different views on same page. Filter, sort, paginate, or, for example, add comment on product page. In this article I'll show how we can mix such multiple views.