django-triggers

django-triggers is intended for implementing event-based business logic configurable through the Django admin site.

Install

pip install dj-triggers

INSTALLED_APPS = [
    ...
    "polymorphic",
    "triggers",
    ...
]

Prerequisites

Celery is required to be setup in your project.

Quickstart

Let's consider a simple tasks app with a model Task and we want to email a user when a task is completed.

1. Add event, action and condition models into your app's models.py

By doing this, we separate the development of the trigger components from their configuration within the Django admin panel. This ensures a more modular and manageable approach to building and configuring triggers.

The full code example is available in tests directory.

from django.dispatch import receiver, Signal
from django.contrib.auth.models import User
from django.db import models, transaction

from triggers.models import Action,  Event


# Our domain model
class Task(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    name = models.CharField(max_length=128)
    is_completed = models.BooleanField(default=False, db_index=True, editable=False)
    is_important = models.BooleanField(default=False)

    completed = Signal()

    def complete(self):
        if not self.is_completed:
            self.is_completed = True
            self.save()
            transaction.on_commit(lambda: self.completed.send(sender=self.__class__, task=self))


# At first, implement an Event which will trigger the notification.
class TaskCompletedEvent(Event):
    # By setting the following `important_only` field through the Django admin site 
    # we can configure what tasks (all or important only) we want to notify the users about.
    important_only = models.BooleanField(
        default=False, 
        help_text='Fire the event for important tasks only if checked.',
    ) 

    def should_be_fired(self, **kwargs) -> bool:
        if self.important_only:
            return Task.objects.filter(id=kwargs['task_id'], is_important=True).exists()
        return True


# Then we need to fire `TaskCompletedEvent` when a task is marked as completed.
@receiver(Task.completed)
def on_task_completed(sender, task: Task, **kwargs):
    for event in TaskCompletedEvent.objects.all():
        transaction.on_commit(lambda: event.fire_single(task.user_id, task_id=task.id))


# At the end, create an Action implementing email notification.
class SendEmailAction(Action):
    subject = models.CharField(max_length=256)
    message = models.TextField()

    def perform(self, user: User, context: Dict[str, Any]):
        user.email_user(self.subject, self.message)

2. Makemigrations and migrate

python manage.py makemigrations
python manage.py migrate

3. Add trigger on the Django admin site

Don't forget to enable it :)

4. Use the trigger!

task = Task.objects.get(id=...)  # Get your task
task.complete()  # And mark it as completed

You may also trigger it manually from the Django admin site if you're checking the test app example.

Development

Run a django-admin command, e.g. makemigrations

poetry run python -m django makemigrations --settings=tests.app.settings

Run isort

poetry run isort triggers tests

Run flake8

poetry run flake8 triggers tests

Run mypy

poetry run mypy triggers tests

Run pytest

poetry run pytest