Tweak caching decorators/utility functions xrefs.

field doesn't exist.

For setting the ``Cache-Control`` and ``Vary`` header fields, it is recommended

to use the :meth:`~django.utils.cache.patch_cache_control` and

:meth:`~django.utils.cache.patch_vary_headers` methods from

to use the :func:`~django.utils.cache.patch_cache_control` and

:func:`~django.utils.cache.patch_vary_headers` methods from

:mod:`django.utils.cache`, since these fields can have multiple, comma-separated

values. The "patch" methods ensure that other values, e.g. added by a

middleware, are not removed.

as a cookie, or a language, or a user-agent -- you'll need to use the ``Vary``

header to tell caching mechanisms that the page output depends on those things.

To do this in Django, use the convenient ``vary_on_headers`` view decorator,

like so::

To do this in Django, use the convenient

:func:`django.views.decorators.vary.vary_on_headers` view decorator, like so::

    from django.views.decorators.vary import vary_on_headers

different from a request with the user-agent ``Mozilla`` and the cookie value

``foo=ham``.

Because varying on cookie is so common, there's a ``vary_on_cookie``

decorator. These two views are equivalent::

Because varying on cookie is so common, there's a

:func:`django.views.decorators.vary.vary_on_cookie` decorator. These two views

are equivalent::

    @vary_on_cookie

    def my_view(request):

The headers you pass to ``vary_on_headers`` are not case sensitive;

``"User-Agent"`` is the same thing as ``"user-agent"``.

You can also use a helper function, ``django.utils.cache.patch_vary_headers``,

You can also use a helper function, :func:`django.utils.cache.patch_vary_headers`,

directly. This function sets, or adds to, the ``Vary header``. For example::

    from django.utils.cache import patch_vary_headers

"private" should be set (and vice versa). An example use of the two directives

would be a blog site that offers both private and public entries. Public

entries may be cached on any shared cache. The following code uses

``patch_cache_control``, the manual way to modify the cache control header

(it is internally called by the ``cache_control`` decorator)::

:func:`django.utils.cache.patch_cache_control`, the manual way to modify the

cache control header (it is internally called by the ``cache_control``

decorator)::

    from django.views.decorators.cache import patch_cache_control

    from django.views.decorators.vary import vary_on_cookie