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Django Activatable Model

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Django Activatable Model

Provides functionality for Django models that have active and inactive states. Features of this app are:

  1. An abstract BaseActivatableModel that allows the user to specify an 'activatable' (i.e. Boolean) field
  2. A model_activations_changed signal that fires when models' activatable field are changed or bulk updated
  3. Validation to ensure activatable models cannot be cascade deleted
  4. Overriding of delete methods so that the activatable flag is set to False instead of the model(s) being deleted (unless force=True)
  5. Manager/QuerySet methods to activate and deactivate models

Installation

pip install django-activatable-model

Add activatable_model to the list of INSTALLED_APPS. Although this app does not define any concrete models, it does connect signals that Django needs to know about.

Basic Usage

Assume you have a model called Account in your app, and it is an activatable model that has a name field and a ForeignKey to a Group model.

from activatable_model.models import BaseActivatableModel

class Account(BaseActivatableModel):
    is_active = models.BooleanField(default=False)
    name = models.CharField(max_length=64)
    group = models.ForeignKey(Group)

By just inheriting BaseActivatableModel, your model will need to define an is_active boolean field (this field name can be changed, more on that later). If you create an Account model, the model_activations_changed signal will be sent with an is_active keyword argument set to False and an instance_ids keyword argument that is a list of the single created account id. Similarly, if you updated the is_active flag at any time via the .save() method, the model_activations_changed signal will be emitted again. This allows the user to do things like this:

from django.dispatch import receiver
from activatable_model import model_activations_changed

@receiver(model_activations_changed, sender=Account)
def do_something_on_deactivation(sender, instance_ids, is_active, **kwargs):
    if not is_active:
        # Either an account was deactivated or an inactive account was created...
        for account in Account.objects.filter(id__in=instance_ids):
            # Do something with every deactivated account

Activatable Model Deletion

Django activatable model is meant for models that should never be deleted but rather activated/deactivated instead. Given the assumption that activatable models should never be deleted, Django activatable model does some magic underneath to ensure your activatable models are properly updated when the user calls .delete(). Instead of deleting the object(s) directly, the is_active flag is set to False and model_activations_changed is fired.

account = Account.objects.create(is_active=True)
account.delete()  # Or Account.objects.all().delete()

# The account still exists
print Account.objects.count()
1

# But it is deactivated
print Account.objects.get().is_active
False

The user can override this behavior by passing force=True to the model or queryset's .delete() method.

Along with overriding deletion, Django activatable model also overrides cascade deletion. No model that inherits BaseActivatableModel can be cascade deleted by another model. This is accomplished by connecting to Django's pre_syncdb signal and verifying that all ForeignKey and OneToOneField fields of activatable models have their on_delete arguments set to something other than the default of models.CASCADE.

In fact, our Account model will not pass validation. In order to make it validate properly on syncdb, it must do the following:

from django.db import models

class Account(BaseActivatableModel):
    is_active = models.BooleanField(default=False)
    name = models.CharField(max_length=64)
    group = models.ForeignKey(Group, on_delete=models.PROTECT)

This will ensure a ProtectedError is thrown every time a Group is deleted. For other options on foreign key deletion behavior, see Django's docs.

Cascade Overrides (new in version 0.8.0 )

As mentioned above, activatable models cannot be cascade deleted. However, this default behavior can be overridden by setting the the class variable, ALLOW_CASCADE_DELETE = True. If set to True, than cascade deletion will be allowed. Note however, that this will be a hard delete, meaning that cascade deletion will completely remove your record from the database rather than applying the ActivatibleModel magic of simply marking it as inactive.

Manager and QuerySet methods

Django activatable models automatically use an ActivatableManager manager that uses an ActivatableQuerySet queryset. This provides the following functionality:

  1. Two methods - activate() and deactivate() that can be applied to a queryset
  2. Overriding the update() method so that it emits model_activations_changed when the is_active flag is updated
  3. Overriding the delete() method so that it calls deactivate() unless force=True

Overriding the activatable field name

The name of the activatable field can be overridden by defining the ACTIVATABLE_FIELD_NAME constant on the model to something else. By default, this constant is set to is_active. An example is as follows:

from activatable_model import BaseActivatableModel

class Account(BaseActivatableModel):
    ACTIVATABLE_FIELD_NAME = 'active'
    active = models.BooleanField(default=False)

In the above example, the model instructs the activatable model app to use active as the activatable field on the model. If the user does not define a BooleanField on the model with the same name as ACTIVATABLE_FIELD_NAME, a ValidationError is raised during syncdb / migrate.

Release Notes

  • 0.5.1

    • Optimize individual saves so that they dont perform an additional query when checking if model activations have been updated
  • 0.5.0

    • Changed the signal to send instance_ids as a keyword argument rather than the instances. This pushes fetching the updated models in signal handlers onto the application
  • 0.4.2

    • Fixed bug when activating a queryset that was filtered by the active flag
  • 0.3.1

    • Added Django 1.7 app config
  • 0.3.0

    • Added Django 1.7 support and backwards compatibility with Django 1.6
  • 0.2.0

    • When upgrading to this version, users will have to explicitly add the is_active field to any models that inherited BaseActivatableModel. This field had a default value of False before, so be sure to add that as the default for the boolean field.

License

MIT License (see the LICENSE file in this repo)

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