Django appregister

Django appregister is a building blocks app to implement a class registry system for your django app. It uses a similar approach to the Django admin, allowing you to register classes and supports an autodiscover feature.

A registry system that provides a good base for making an app plugable and extendable by third parties as they can register their own subclasses for Use within the main code base.

Installation

Use pip:

pip install django-appregister

Quick Example Usage

First, you should create your base class that all registered classes must be a subclass of. Often this is a base Model class in your models.py or it can be anywhere in your project:

>>> class AppPlugin(object):
...     pass

Then you need to create your own registry, the base can either be a class, or a dotted string that points to the base class, such as "myapp.AppPlugin". After that, you can go ahead and create an instance of the registry - creating it at the module level makes it easy to re-use across the project but you can have as many instances as you need. It’s good practice to create your registry in its own module, such as myapp/register.py:

>>> from appregister import Registry

>>> class MyRegistry(Registry):
...     base = AppPlugin
...     discovermodule = 'plugins'

>>> plugins = MyRegistry()

Now that you have the registry, you can start to add subclasses to it. This can be done by using the class decorator on your register:

>>> @plugins.register
... class MyPlugin(AppPlugin):
...     pass

Note, If you are using version 2.5 or below of Python you can’t use the class based decorator, you will need to call it manually. The above example would then become:

>>> class MySecondPlugin(AppPlugin):
...     pass
>>> plugins.register(MySecondPlugin)
<class 'MySecondPlugin'>

Registering an invalid object will raise an InvalidOperation exception:

>>> # Note that this class does not inherit from the base we specified.
>>> class MyNonSubclass(object):
...     pass

>>> plugins.register(MyNonSubclass)
Traceback (most recent call last):
    ...
InvalidOperation: Object 'MyNonSubclass' is not a subclass of 'AppPlugin'

Finally, now you can get all your objects back - this includes those registered by a third party:

>>> len(plugins)
2

>>> for plugin in plugins:
...     print plugin
<class 'MySecondPlugin'>
<class 'MyPlugin'>

The order of registration is not stored. Since we can’t tell what order they would be registered, if you want a sorted set you will need to sort them after they have all been registered:

>>> plugins.clear()
>>> len(plugins)
0