django-mobile

django-mobile provides a simple way to detect mobile browsers and gives you tools at your hand to render some different templates to deliver a mobile version of your site to the user.

The idea is to keep your views exactly the same but to transparently interchange the templates used to render a response. This is done in two steps:

A middleware determines the client's preference to view your site. E.g. if he wants to use the mobile flavour or the full desktop flavour.
The template loader takes then care of choosing the correct templates based on the flavour detected in the middleware.

Installation

Pre-Requirements: django_mobile depends on django's session framework. So before you try to use django_mobile make sure that the sessions framework is enabled and working.

Install django_mobile with your favourite python tool, e.g. with easy_install django_mobile or pip install django_mobile.
Add django_mobile to your INSTALLED_APPS setting in the settings.py.
Add django_mobile.middleware.MobileDetectionMiddleware to your MIDDLEWARE_CLASSES setting.
Add django_mobile.middleware.SetFlavourMiddleware to your MIDDLEWARE_CLASSES setting. Make sure it's listed after MobileDetectionMiddleware and also after SessionMiddleware.
Add django_mobile.loader.Loader as first item to your TEMPLATE_LOADERS list in settings.py.
Add django_mobile.context_processors.flavour to your TEMPLATE_CONTEXT_PROCESSORS setting.

Now you should be able to use django-mobile in its glory. Read below of how things work and which settings can be tweaked to modify django-mobile's behaviour.

Usage

The concept of django-mobile is build around the ideas of different flavours for your site. For example the mobile version is described as one possible flavour, the desktop version as another.

This makes it possible to provide many possible designs instead of just differentiating between a full desktop experience and one mobile version. You can make multiple mobile flavours available e.g. one for mobile safari on the iPhone and Android as well as one for Opera and an extra one for the internet tablets like the iPad.

Note: By default django-mobile only distinguishes between full and mobile flavour.

After the correct flavour is somehow chosen by the middlewares, it's assigned to the request.flavour attribute. You can use this in your views to provide separate logic.

This flavour is then use to transparently choose custom templates for this special flavour. The selected template will have the current flavour prefixed to the template name you actually want to render. This means when render_to_response('index.html', ...) is called with the mobile flavour being active will actually return a response rendered with the mobile/index.html template. However if this flavoured template is not available it will gracefully fallback to the default index.html template.

In some cases its not the desired way to have a completely separate templates for each flavour. You can also use the {{ flavour }} template variable to only change small aspects of a single template. A short example:

<html>
<head>
    <title>My site {% if flavour == "mobile" %}(mobile version){% endif %}</title>
</head>
<body>
    ...
</body>
</html>

This will add (mobile version) to the title of your site if viewed with the mobile flavour enabled.

Note: The flavour template variable is only available if you have set up the django_mobile.context_processors.flavour context processor and used django's RequestContext as context instance to render the template.

Changing the current flavour

The basic use case of django-mobile is obviously to serve a mobile version of your site to users. The selection of the correct flavour is usually already done in the middlewares when your own views are called. In some cases you want to change the currently used flavour in your view or somewhere else. You can do this by simply calling django_mobile.set_flavour(flavour[, permanent=True]). The first argument is self explaining. But keep in mind that you only can pass in a flavour that you is also in your FLAVOURS setting. Otherwise set_flavour will raise a ValueError. The optional permanent parameters defines if the change of the flavour is remember for future requests of the same client.

Your users can set their desired flavour them self. They just need to specify the flavour GET parameter on a request to your site. This will permanently choose this flavour as their preference to view the site.

You can use this GET parameter to let the user select from your available flavours:

<ul>
    <li><a href="?flavour=full">Get the full experience</a>
    <li><a href="?flavour=mobile">View our mobile version</a>
    <li><a href="?flavour=ipad">View our iPad version</a>
</ul>

Notes on caching

Django is shipping with some convenience methods to easily cache your views. One of them is django.views.decorators.cache.cache_page. The problem with caching a whole page in conjunction with django-mobile is, that django's caching system is not aware of flavours. This means that if the first request to a page is served with a mobile flavour, the second request might also get a page rendered with the mobile flavour from the cache -- even if the second one was requested by a desktop browser.

django-mobile is shipping with it's own implementation of cache_page to resolve this issue. Please use django_mobile.cache.cache_page instead of django's own cache_page decorator.

You can also use django's caching middlewares django.middleware.cache.UpdateCacheMiddleware and FetchFromCacheMiddleware like you already do. But to make them aware of flavours, you need to add django_mobile.cache.middleware.CacheFlavourMiddleware as second last item in the MIDDLEWARE_CLASSES settings, right before FetchFromCacheMiddleware.

Template caching If you are using Django's cached template loader <https://docs.djangoproject.com/en/dev/ref/templates/api/#loader-types> the django_mobile.loader.Loader template loader will not work properly.

To use cached template loader and django_mobile switch to the included django_mobile.loader.CachedLoader.

In your settings.py include the template loaders like this:

TEMPLATE_LOADERS = (
    ('django_mobile.loader.CachedLoader', (
        'django.template.loaders.filesystem.Loader',
        'django.template.loaders.app_directories.Loader',
        'django.template.loaders.eggs.Loader',
    )),
)

Note: the FLAVOURS_TEMPLATE_LOADERS setting has no effect when using django_mobile.loader.CachedLoader.

Reference

django_mobile.get_flavour([request,] [default])

Get the currently active flavour. If no flavour can be determined it will return default. This can happen if set_flavour was not called before in the current request-response cycle. default defaults to the first item in the FLAVOURS setting.

django_mobile.set_flavour(flavour, [request,] [permanent])

Set the flavour to be used for request. This will raise ValueError if flavour is not in the FLAVOURS setting. You can try to set the flavour permanently for request by passing permanent=True. This may fail if you are out of a request-response cycle. request defaults to the currently active request.

django_mobile.context_processors.flavour

Context processor that adds the current flavour as flavour to the context.

django_mobile.context_processors.is_mobile

This context processor will add a is_mobile variable to the context which is True if the current flavour equals the DEFAULT_MOBILE_FLAVOUR setting.

django_mobile.middleware.SetFlavourMiddleware

Takes care of loading the stored flavour from the user's session if set. Also sets the current request to a thread-local variable. This is needed to provide get_flavour() functionality without having access to the request object.

django_mobile.middleware.MobileDetectionMiddleware

Detects if a mobile browser tries to access the site and sets the flavour to DEFAULT_MOBILE_FLAVOUR settings value in case.

django_mobile.cache.cache_page

Same as django's cache_page decorator but applies vary_on_flavour before the view is decorated with django.views.decorators.cache.cache_page.

django_mobile.cache.vary_on_flavour

A decorator created from the CacheFlavourMiddleware middleware.

django_mobile.cache.middleware.CacheFlavourMiddleware

Adds X-Flavour header to request.META in process_request and adds this header to response['Vary'] in process_response.

Customization

There are some points available that let you customize the behaviour of django-mobile. Here are some possibilities listed:

`MobileDetectionMiddleware`

The built-in middleware to detect if the user is using a mobile browser served well in production but is far from perfect and also implemented in a very simplistic way. You can safely remove this middleware from your settings and add your own version instead. Just make sure that it calls django_mobile.set_flavour at some point to set the correct flavour for you.

Settings

Here is a list of settings that are used by django-mobile and can be changed in your own settings.py:

FLAVOURS

A list of available flavours for your site.

Default: ('full', 'mobile')

DEFAULT_MOBILE_FLAVOUR

The flavour which is chosen if the built-in MobileDetectionMiddleware detects a mobile browser.

Default: mobile

FLAVOURS_TEMPLATE_PREFIX

This string will be prefixed to the template names when searching for flavoured templates. This is useful if you have many flavours and want to store them in a common subdirectory. Example:

from django.template.loader import render_to_string
from django_mobile import set_flavour

set_flavour('mobile')
render_to_string('index.html') # will render 'mobile/index.html'

# now add this to settings.py
FLAVOURS_TEMPLATE_PREFIX = 'flavours/'

# and try again

set_flavour('mobile')
render_to_string('index.html') # will render 'flavours/mobile/index.html'

Default: '' (empty string)

FLAVOURS_TEMPLATE_LOADERS

django-mobile's template loader can load templates prefixed with the current flavour. Specify with this setting which loaders are used to load flavoured templates.

Default: same as TEMPLATE_LOADERS setting but without 'django_mobile.loader.Loader'.

FLAVOURS_GET_PARAMETER

Users can change the flavour they want to look at with a HTTP GET parameter. This determines the name of this parameter. Set it to None to disable.

Default: 'flavour'

FLAVOURS_SESSION_KEY

The user's preference set with the GET parameter is stored in the user's session. This setting determines which session key is used to hold this information.