django-activatable-model 3.1.0
Django Activatable Model
License: MIT
Keywords: Django,Model,Activatable

[![Build Status](https://travis-ci.org/ambitioninc/django-activatable-model.png)](https://travis-ci.org/ambitioninc/django-activatable-model)
# 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
1. A model_activations_changed signal that fires when models' activatable field
are changed or bulk updated
1. Validation to ensure activatable models cannot be cascade deleted
1. Overriding of delete methods so that the activatable flag is set to False 
instead of the model(s) being deleted (unless force=True)
1. Manager/QuerySet methods to activate and deactivate models

## Installation
```bash
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.

```python
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:

```python
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.

```python
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:

```python
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](https://docs.djangoproject.com/en/1.7/ref/models/fields/#django.db.models.ForeignKey.on_delete).

### 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
1. Overriding the `update()` method so that it emits 
`model_activations_changed` when the `is_active` flag is updated
1. 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:

```python
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](LICENSE) file in this repo)