django-logical-rules 1.0

A rule engine for Django apps.

A tool to manage logical rules throughout your application. Logical rules are more powerful than permission or rule tables because they are written in python. Register a rule once and work with it throughout your app, from templates to generic view mixins. Instead of cluttering your models with rule-style and permission-style methods define those rules in rules.py and then get easy access to them in your views and templates.

Installation

Use pip to install from PyPI:

pip install django-logical-rules

Add logical_rules to your settings.py file:

INSTALLED_APPS = (
    ...
    'logical_rules',
    ...
)

Additional Requirements

If you want to use the messaging features install Django messages framework.

Configuration

Rules are defined in rules.py files within your apps. Here’s an example of a rule:

import logical_rules

def user_can_edit_mymodel(object, user):
        """
                Confirms a user can edit a specific model
                ...owners only!
        """
        return object.owner == user
logical_rules.site.register("user_can_edit_mymodel", user_can_edit_mymodel)

To include your models in the registry you will need to do run the autodiscover, a bit like django.contrib.admin (I generally put this in urls.py):

import logical_rules
logical_rules.autodiscover()

Usage

Template Tag

Once you have created a rule, it’s easy to use anywhere in your templates:

{% load logical_rules_tags %}
{% testrule user_can_edit_mymodel object request.user %}
        <p>You are the owner!</p>
{% endtestrule %}

Note: Don’t use quotes around the rule name in the template.

RulesMixin

If you are extending Django’s class-based generic views, you might find this mixin useful. It allows you to define rules that should be applied before rendering a view. Here’s an example usage:

class MyView(RulesMixin, DetailView):

   def update_logical_rules(self):
      super(MyView, self).update_logical_rules()
      self.add_logical_rule({
         'name': 'user_can_edit_mymodel',
         'param_callbacks': [
            ('object', 'get_object'),
            ('user', 'get_request_user')
         ]
      })

param_callbacks are our technique for getting the parameters for your rule. These are assumed to be methods on your class. get_request_user() is defined in RuleMixin since it’s so common. get_object() is a method on the DetailView class.

Rule dictionaries can have other properties, like redirect_url and response_callback. If redirect_url is defined, then the view will return an HttpResponseRedirect to that URL. If response_callback is defined, then the view will return the result of that method.

Messaging integration is possible with message and message_level options.

Finally, we’ve added two commonly used rules. As an optional substitute for login_required, we have user_is_authenticated and to test a generic expression, we have evaluate_expression.

Direct Calling

import logical_rules
if logical_rules.site.test_rule(rule['name'], arg1, arg2):
        print "passed"
else:
        print "failed"

Contributing

Think this needs something else? To contribute to django-logical-rules create a fork on Bitbucket. Clone your fork, make some changes, and submit a pull request.

Bugs are great contributions too! Feel free to add an issue on Bitbucket: