All By Myself - Django Singletons

Singletons are objects that can only be instantiated once and serve a specific purpose. A classic example of where a singleton is necessary in web development is site configuration. This package provides an abstract singleton base model, SingletonBaseModel, along with a model admin, SingletonBaseModelAdmin, both of which are utilized to create and manage singleton objects in Django.

Installation

$ pip install django-allbymyself

Quick Start

Add to INSTALLED_APPS in your project's settings.py to load custom admin templates:

INSTALLED_APPS = [
    ...
    'allbymyself',
]

Create a model in your_app/models.py and subclass SingletonBaseModel:

from django.db import models
from allbymyself.models import SingletonBaseModel

class SiteSettings(SingletonBaseModel):
    site_title = models.CharField(max_length=50)
    about = models.CharField(max_length=255)

Register the model in your_app/admin.py, subclassing SingletonBaseModelAdmin:

from django.contrib import admin
from allbymyself.admin import SingletonBaseModelAdmin
from your_app.models import SiteSettings

@admin.register(SiteSettings)
class SiteSettingsAdmin(SingletonBaseModelAdmin):
    fields = ('site_title', 'about')

Features

• Skips change list page and instead goes straight to the change form or add form.
• SingletonBaseModel handles caching and uncaching.
• Admin URLs for change form and history form will not include object id.
• After saving changes or adding a new instance, the admin user is redirected to the admin index.
• Override is_default_available and return True to create an instance on admin page startup:

class SiteSettings(SingletonBaseModel):
    site_title = models.CharField(max_length=50, blank=True)
    about = models.CharField(max_length=255, blank=True)

    @classmethod
    def is_default_available(cls):
        # if True, make sure to handle field defaults in your model
        # appropriately!
        return True

Context Processor

You may also add your object as a context processor to make it available in all templates, site-wide. First create your_app/context_processors.py and add the following:

from django.urls import reverse
from your_app.models import SiteSettings

def site_settings(request):
    if request.path.startswith(reverse('admin:index')):
        return {}
    else:
        return {'site_settings': SiteSettings.get()}

The above if statement prevents creation of an instance on admin page startup. This is only necessary if is_default_available returns False. Then, in your project's settings.py:

TEMPLATES = [
    {
        ...
        'OPTIONS': {
            'context_processors': [
                ...
                'your_app.context_processors.site_settings',
            ],
        },
    },
]

You can then access your object in your templates like any other piece of context:

<h1>{{ site_settings.site_title }}</h1>
<p>{{ site_settings.about }}</p>

Testing

Simply run tests like so:

$ python manage.py test allbymyself