Django Solo
===========

<a href="https://pypi.org/project/django-solo/" alt="Current version on PyPi"><img src="https://img.shields.io/pypi/v/django-solo.svg" /></a>


    +---------------------------+
    |                           |
    |                           |
    |             \             | Django Solo helps working with singletons:
    |             /\            | database tables that only have one row.
    |           >=)'>           | Singletons are useful for things like global
    |             \/            | settings that you want to edit from the admin
    |             /             | instead of having them in Django settings.py.
    |                           | 
    |                           | 
    +---------------------------+


Features
--------

Solo helps you enforce instantiating only one instance of a model in django.

* You define the model that will hold your singleton object.
* django-solo gives helper parent class for your model and the admin classes.
* You get an admin interface that's aware you only have one object.
* You can retrieve the object from templates.
* By enabling caching, the database is not queried intensively.

Use Cases
--------

Django Solo is also great for use with singleton objects that have a one to many relationship. Like the use case below where you have a 'Home Slider" that has many "Slides".

* Global or default settings
* An image slider that has many slides
* A page section that has sub-sections
* A team bio with many team members

There are many cases where it makes sense for the parent in a one to many relationship to be limited to a single instance.

Usage Example

```python
# models.py

from django.db import models
from django_solo.models import SingletonModel


class SiteConfiguration(SingletonModel):
    site_name = models.CharField(max_length=255, default='Site Name')
    maintenance_mode = models.BooleanField(default=False)

    def __str__(self):
        return "Site Configuration"

    class Meta:
        verbose_name = "Site Configuration"
```

```python
# admin.py

from django.contrib import admin
from django_solo.admin import SingletonModelAdmin
from config.models import SiteConfiguration


admin.site.register(SiteConfiguration, SingletonModelAdmin)
```

```python
# There is only one item in the table, you can get it this way:
from .models import SiteConfiguration
config = SiteConfiguration.objects.get()

# get_solo will create the item if it does not already exist
config = SiteConfiguration.get_solo()
```

In your model, note how you did not have to provide a `verbose_name_plural` field -
That's because Django Solo uses the `verbose_name` instead.

If you're changing an existing model (which already has some objects stored in the database) to a singleton model, you can explicitly provide the id of the row in the database for django-solo to use. This can be done by setting `singleton_instance_id` property on the model:

```python
class SiteConfiguration(SingletonModel):
    singleton_instance_id = 24
    # (...)
```

Installation
------------

This application requires Django 3.2, 4.0, or 4.1.

* Install the package using `pip install django-solo`
* Add ``django_solo`` or ``django_solo.apps.SoloAppConfig`` to your ``INSTALLED_APPS`` setting.

This is how you run tests:

    ./manage.py test django_solo --settings=django_solo.tests.settings

And from within `tox`:

```
python -m pip install tox
tox
```

Supported Languages
-------------------

- English
- Spanish
- German

Admin
-----

The standard Django admin does not fit well when working with singleton,
for instance, if you need some global site settings to be edited in the admin.
Django Solo provides a modified admin for that.


![django-solo admin](https://raw.github.com/lazybird/django-solo/master/docs/images/django-solo-admin.jpg "django-solo admin")


* In the admin home page where all applications are listed, we have a `config`
  application that holds a singleton model for site configuration.
* The configuration object can only be changed, there's no link for "add" (1).
* The link to the configuration page (2) directly goes to the form page - no
  need for an intermediary object list page, since there's only one object.
* The edit page has a modified breadcrumb (3) to avoid linking to the
  intermediary object list page.
* From the edit page, we cannot delete the object (4) nor can we add a new one (5).

If you wish to disable the skipping of the object list page, and have the default
breadcrumbs, you should set `SOLO_ADMIN_SKIP_OBJECT_LIST_PAGE` to `False` in your settings.

Availability from templates
---------------------------

The singleton object can be retrieved from template by giving the Django model
dotted path:

```django
{% get_solo 'app_label.ModelName' as my_config %}
```

Example:

```django
{% load solo_tags %}
{% get_solo 'config.SiteConfiguration' as site_config %}
{{ site_config.site_name }}
{{ site_config.maintenance_mode }}
```

If you're extending a template, be sure to use the tag in the proper scope.

Right:

```django
{% extends "index.html" %}
{% load solo_tags %}

{% block content %}
    {% get_solo 'config.SiteConfiguration' as site_config %}
    {{ site_config.site_name }}
{% endblock content %}
```

Wrong:

```django
{% extends "index.html" %}
{% load solo_tags %}
{% get_solo 'config.SiteConfiguration' as site_config %}

{% block content %}
    {{ site_config.site_name }}
{% endblock content %}
```


Caching
-------

By default caching is disabled: every time `get_solo` retrieves the singleton
object, there will be a database query.

You can enable caching to only query the database when initially retrieving the
object. The cache will also be updated when updates are made from the admin.

The cache timeout is controlled via the `SOLO_CACHE_TIMEOUT` settings.
The cache backend to be used is controlled via the `SOLO_CACHE` settings.


Settings
--------

### Template tag name

You can retrieve your singleton object in templates using the `get_solo`
template tag.

You can change the name `get_solo` using the
`GET_SOLO_TEMPLATE_TAG_NAME` setting.

```python
GET_SOLO_TEMPLATE_TAG_NAME = 'get_config'
```

### Admin override flag

By default, the admin is overridden. But if you wish to keep the object list
page (e.g. to customize actions), you can set the `SOLO_ADMIN_SKIP_OBJECT_LIST_PAGE`
to `False`.

```python
SOLO_ADMIN_SKIP_OBJECT_LIST_PAGE = True
```

### Cache backend

Django provides a way to define multiple cache backends with the `CACHES`
settings. If you want the singleton object to be cached separately, you
could define the `CACHES` and the `SOLO_CACHE` settings like this:

```python
CACHES = {
    'default': {
        'BACKEND': 'django.core.cache.backends.memcached.MemcachedCache',
        'LOCATION': '127.0.0.1:11211',
    },
    'local': {
        'BACKEND': 'django.core.cache.backends.locmem.LocMemCache',
    },
}

SOLO_CACHE = 'local'
```

Caching will be disabled if set to `None`.


### Cache timeout

The cache timeout in seconds.

```python
SOLO_CACHE_TIMEOUT = 60*5  # 5 mins
```

### Cache prefix

The prefix to use for the cache key.

```python
SOLO_CACHE_PREFIX = 'solo'
```

Getting the code
================

The code is hosted at https://github.com/lazybird/django-solo/

Check out the latest development version anonymously with:

    $ git clone git://github.com/lazybird/django-solo.git

You can install the package in the "editable" mode like this:

    pip uninstall django-solo  # just in case...
    pip install -e git+https://github.com/lazybird/django-solo.git#egg=django-solo

You can also install a specific branch:

    pip install -e git+https://github.com/lazybird/django-solo.git@my-branch#egg=django-solo

The package is now installed in your project and you can find the code.

To run the unit tests:

    pip install tox
    tox

### Making a release

1. Update [`solo/__init__.py`](solo/__init__.py) `version`

2. Update [`CHANGES`](./CHANGES)

3. Make a new release on GitHub

4. Upload release to PyPI

```shell
tox -e build
```

```shell
tox -e upload
```