Django Business Rules

Overview

With this plugin django users (customers or administrators) can setup business rules with html forms. Default layout is similar to django admin panel and can be easily overridden.
Business rules engine is implemented with business-rules

Requirements

• Python (2.7, 3.4, 3.5, 3.6, 3.7)
• Django (1.9, 1.10, 1.11, 2.0.7)

Installation

Install using pip…

pip install django-business-rules

Add 'django_business_rules' to your INSTALLED_APPS setting.

INSTALLED_APPS = (
    ...
    'django_business_rules',
)

Example

Let’s take a look at a quick example of using Business rules plugin.

Setup

Startup up a new project like so…

pip install django django-business-rules
django-admin.py startproject example .
./manage.py startapp test_app

Now edit the example/urls.py module in your project (django 2.x):

from django.urls import include, path, re_path

# Include the business rules URLconf
urlpatterns = [
    ...
    re_path(r'^dbr/', include('django_business_rules.urls', namespace='django_business_rules'))
]

Now edit the example/urls.py module in your project (django 1.x):

from django.conf.urls import include, url

# Include the business rules URLconf
urlpatterns = [
    ...
    url(r'^dbr/', include('django_business_rules.urls', namespace='django_business_rules'))
]

Add the following to your example/settings.py module:

INSTALLED_APPS = (
    ...  # Make sure to include the default installed apps here.
    'django_business_rules',
    'test_app.apps.TestAppConfig',
)

Usage

Add models to your test_app/model.py module:

from django.db import models


class Product(models.Model):
    name = models.TextField()
    related_products = models.ManyToManyField('Product', blank=True)
    current_inventory = models.IntegerField(default=0)
    price = models.IntegerField(default=0)

    @property
    def orders(self):
        return list(self.productorder_set.all())


class ProductOrder(models.Model):
    expiration_date = models.DateField()
    quantity = models.IntegerField(default=0)
    product = models.ForeignKey(Product, on_delete=models.CASCADE)

Add variables and actions to your test_app/rules.py module (more about variables and actions can be found here):

import datetime

from business_rules.actions import BaseActions, rule_action
from business_rules.fields import FIELD_NUMERIC
from business_rules.variables import BaseVariables, numeric_rule_variable, \
    string_rule_variable, select_rule_variable
from django.utils import timezone
from django_business_rules.business_rule import BusinessRule

from test_app.models import Product, ProductOrder


class ProductVariables(BaseVariables):

    def __init__(self, product):
        self.product = product

    @numeric_rule_variable
    def current_inventory(self):
        return self.product.current_inventory

    @numeric_rule_variable(label='Days until expiration')
    def expiration_days(self):
        last_order = self.product.orders[-1]
        expiration_days = (last_order.expiration_date - datetime.date.today()).days
        return expiration_days

    @string_rule_variable()
    def current_month(self):
        return timezone.now().strftime('%B')


class ProductActions(BaseActions):

    def __init__(self, product):
        self.product = product

    @rule_action(params={'sale_percentage': FIELD_NUMERIC})
    def put_on_sale(self, sale_percentage):
        self.product.price *= (1.0 - sale_percentage)
        self.product.save()

    @rule_action(params={'number_to_order': FIELD_NUMERIC})
    def order_more(self, number_to_order):
        ProductOrder.objects.create(
            product=self.product,
            quantity=number_to_order,
            expiration_date=timezone.now() + timezone.timedelta(weeks=4)
        )


class ProductBusinessRule(BusinessRule):
    name = 'Product rules'
    variables = ProductVariables
    actions = ProductActions

Add triggering defined rules on django post_save signal to your test_app/signals.py module:

from django.db.models.signals import post_save
from django.dispatch import receiver

from test_app.models import Product
from test_app.rules import ProductBusinessRule


@receiver(post_save, sender=Product)
def execute_product_business_rules(sender, instance, **kwargs):
    ProductBusinessRule.run_all(instance)

Register signals in test_app/apps.py module:

class TestAppConfig(AppConfig):
    name = 'test_app'

    def ready(self):
        import test_app.signals

Create and execute migrations:

./manage.py makemigrations
./manage.py migrate

Generate business rules (currently this command doesn’t support updates, previously stored business rules data will be overridden):

./manage.py dbr

That’s it, we’re done!

./manage.py runserver

You can now open the list of business rules in your browser at http://127.0.0.1:8000/dbr/business-rule/ and edit them.

Contribution

Open up a pull request, making sure to add tests for any new functionality. To set up the dev environment (assuming you’re using virtualenvwrapper and docker):

$ mkvirtualenv django-business-rules
$ pip install -r dbr/requirements-development.txt
$ pip install -r dbr/requirements-django1.11.txt # (for python 2.7)
$ pip install -r dbr/requirements-django2.0.txt # (for python 3)
$ ./test.sh
$ ./build.sh