=============
Configuration
=============

Mezzanine provides a central system for defining settings within
your project and applications that can then be edited by admin users.
The package ``mezzanine.conf`` contains the models for storing
editable settings in the database as well as the functions for
registering and loading these settings throughout your project.

.. _registering-settings:

Registering Settings
====================

Settings are defined by creating a module named ``defaults.py`` inside
one or more of the applications defined in your project's
``settings.INSTALLED_APPS`` setting. Inside your ``defaults.py`` module
you then call the function ``mezzanine.conf.register_setting`` for
each setting you want to define which takes several keyword arguments:

  * ``name``: The name of the setting.
  * ``description``: The description of the setting.
  * ``editable``: If ``True``, the setting will be editable via the admin.
  * ``default``: The default value of the setting.
  * ``choices``: A list of choices the user can select from when the
    setting is editable.
  * ``append``: If registering an existing setting, the default value
    given will be appended to the current.

.. note::

    For settings registered with ``editable`` as ``True``, currently only
    strings, integers/floats and boolean values are supported for the
    ``default`` value.

For example suppose we had a ``authors`` application and we wanted to
create a setting that controls the number of books displayed per author
page, we would define the following in ``authors.defaults``::

    from mezzanine.conf import register_setting

    register_setting(
        name="AUTHORS_BOOKS_PER_PAGE",
        description="The number of books to show per author page.",
        editable=True,
        default=10,
    )

Reading Settings
================

Mezzanine provides a settings object via ``mezzanine.conf.settings`` in a
similar way to Django's ``django.conf.settings``. This settings object
contains each of the settings registered above using their names as
attributes. The settings object also contains the method ``use_editable``
which when called will cause the settings object to reload editable settings
from the database the next time an editable setting is accessed. Continuing
on from our previous example, suppose we have a view for photos::

    from django.shortcuts import render
    from mezzanine.conf import settings
    from .models import Book

    def books_view(request):
        settings.use_editable()
        books = Book.objects.all()[:settings.AUTHORS_BOOKS_PER_PAGE]
        return render(request, "books.html", {"books": books})

When defining editable settings, care should be taken when considering
where in your project the setting will be used. For example if a setting
is used in a ``urlpattern`` or the creation of a ``model`` class it would
only be read when your site is first loaded, and therefore having it
change at a later point by an admin user would not have any effect without
reloading your entire project. In the snippet above by calling
``settings.use_editable()`` within the view, the value of the setting being
accessed is loaded each time the view is run. This ensures that if the value
of the setting has been changed by an admin user it will be reflected on the
website.

.. note::

    It's also important to realize that with any settings flagged as
    editable, defining a value for these in your project's
    ``settings.py`` will only serve to provide their default values.
    Once editable settings are modified via the admin, their values
    stored in the database will always be used.

Django Settings
===============

Mezzanine's settings object integrates with Django's settings object in a
couple of ways.

Firstly it's possible to override the default value for any setting defined
using ``mezzanine.conf.register_setting`` by adding its name and value as
a regular setting to your project's settings module. This is especially useful
when any of your project's ``INSTALLED_APPS`` (including Mezzanine
itself) register settings that aren't editable and you want to override
these settings without modifying the application that registered them.

Secondly it's possible to access any of the settings defined by Django or
your project's settings module via Mezzanine's settings object in the same
way you would use Django's settings object. This allows for a single access
point for all settings regardless of how they are defined.

Default Settings
================

Mezzanine defines the following settings:

.. include:: settings.rst