root/django/branches/0.90-bugfixes/docs/generic_views.txt

===================
Using generic views
===================

Writing Web applications can be monotonous, because we repeat certain patterns
again and again. In Django, the most common of these patterns have been
abstracted into "generic views" that let you quickly provide common views of
an object without actually needing to write any views.

Django's generic views contain the following:

    * A set of views for doing list/detail interfaces (for example,
      Django's `documentation index`_ and `detail pages`_).

    * A set of views for year/month/day archive pages and associated
      detail and "latest" pages (for example, the Django weblog's year_,
      month_, day_, detail_, and latest_ pages).

    * A set of views for creating, editing, and deleting objects.

.. _`documentation index`: http://www.djangoproject.com/documentation/
.. _`detail pages`: http://www.djangoproject.com/documentation/faq/
.. _year: http://www.djangoproject.com/weblog/2005/
.. _month: http://www.djangoproject.com/weblog/2005/jul/
.. _day: http://www.djangoproject.com/weblog/2005/jul/20/
.. _detail: http://www.djangoproject.com/weblog/2005/jul/20/autoreload/
.. _latest: http://www.djangoproject.com/weblog/

All of these views are used by creating configuration dictionaries in
your URLconf files and passing those dictionaries as the third member of the
URLconf tuple. For example, here's the URLconf for the simple weblog app that
drives the blog on djangoproject.com::

    from django.conf.urls.defaults import *

    info_dict = {
        'app_label': 'blog',
        'module_name': 'entries',
        'date_field': 'pub_date',
    }

    urlpatterns = patterns('django.views.generic.date_based',
       (r'^(?P<year>\d{4})/(?P<month>[a-z]{3})/(?P<day>\w{1,2})/(?P<slug>\w+)/$', 'object_detail', dict(info_dict, slug_field='slug')),
       (r'^(?P<year>\d{4})/(?P<month>[a-z]{3})/(?P<day>\w{1,2})/$',               'archive_day',   info_dict),
       (r'^(?P<year>\d{4})/(?P<month>[a-z]{3})/$',                                'archive_month', info_dict),
       (r'^(?P<year>\d{4})/$',                                                    'archive_year',  info_dict),
       (r'^/?$',                                                                  'archive_index', info_dict),
    )

As you can see, this URLconf defines a few options in ``info_dict`` that tell
the generic view which model to use (``blog.entries`` in this case), as well as
some extra information.

Documentation of each generic view follows, along with a list of all keyword
arguments that a generic view expects. Remember that as in the example above,
arguments may either come from the URL pattern (as ``month``, ``day``,
``year``, etc. do above) or from the additional-information dictionary (as for
``app_label``, ``module_name``, etc.).

Most of the generic views that follow require the ``app_label`` and
``module_name`` keys. These values are easiest to explain through example::

    >>> from django.models.blog import entries

In the above line, ``blog`` is the ``app_label`` (the name of the file that
holds all your model definitions) and ``entries`` is the ``module_name``
(either a pluralized, lowercased version of the model class name, or the value
of the ``module_name`` option of your model). In the docs below, these keys
will not be repeated, but each generic view requires them.

Using "simple" generic views
============================

The ``django.views.generic.simple`` module contains simple views to handle a
couple of common cases: rendering a template when no view logic is needed,
and issuing a redirect.  These views are:

``direct_to_template``
    Renders a given template, passing it a ``{{ params }}`` template variable,
    which is a dictionary of the parameters captured in the URL. This requires
    the ``template`` argument.

    For example, given the following URL patterns::

        urlpatterns = patterns('django.views.generic.simple',
            (r'^foo/$',             'direct_to_template', {'template': 'foo_index'}),
            (r'^foo/(?P<id>\d+)/$', 'direct_to_template', {'template': 'foo_detail'}),
        )

    ... a request to ``/foo/`` would cause the ``foo_index`` template to be
    rendered, and a request to ``/foo/15/`` would cause the ``foo_detail``
    template to be rendered with a context variable ``{{ params.id }}`` that is
    set to ``15``.

``redirect_to``
    Issue a redirect to a given URL.

    The given URL may contain dict-style string formatting, which will be
    interpolated against the params in the URL.  For example, to redirect from
    ``/foo/<id>/`` to ``/bar/<id>/``, you could use the following urlpattern::

        urlpatterns = patterns('django.views.generic.simple',
            ('^foo/(?p<id>\d+)/$', 'redirect_to', {'url' : '/bar/%(id)s/'}),
        )

    If the given URL is ``None``, an ``HttpResponseGone`` (410) will be issued.

Using date-based generic views
==============================

Date-based generic views (in the module ``django.views.generic.date_based``)
feature six functions for dealing with date-based data. Besides ``app_label``
and ``module_name``, all date-based generic views require that the
``date_field`` argument be passed to them. This is the name of the field that
stores the date the objects should key off of.

Additionally, all date-based generic views have the following optional
arguments:

    =======================  ==================================================
    Argument                 Description
    =======================  ==================================================
    ``template_name``        Overrides the default template name used for the
                             view.

    ``extra_lookup_kwargs``  A dictionary of extra lookup parameters (see
                             the `database API docs`_).

    ``extra_context``        A dictionary of extra data to put into the
                             template's context.
    =======================  ==================================================

.. _`database API docs`: http://www.djangoproject.com/documentation/db_api/

The date-based generic functions are:

``archive_index``
    A top-level index page showing the "latest" objects. Has an optional
    argument, ``num_latest``, which is the number of items to display on the
    page (defaults to 15).

    Uses the template ``app_label/module_name_archive`` by default.

    Has the following template context:

        ``date_list``
            List of years with objects
        ``latest``
            Latest objects by date

``archive_year``
    Yearly archive. Requires that the ``year`` argument be present in the URL
    pattern.

    Uses the template ``app_label/module_name_archive_year`` by default.

    Has the following template context:

        ``date_list``
            List of months in the given year with objects
        ``year``
            The given year (an integer)

``archive_month``
    Monthly archive. Requires that ``year`` and ``month`` arguments be given.
    You can pass the additional option ``month_format`` if you'd like to change
    the way months are specified in the URL.

    ``month_format`` is a format string in the same syntax accepted by Python's
    ``time.strftime``. (See the `strftime docs`_.) It's set to ``"%b"`` by
    default, which is a three-letter month abbreviation. To change it to use
    numbers, use ``"%m"``.

    Uses the template ``app_label/module_name_archive_month`` by default.

    Has the following template context:

        ``month``
            The given month (a datetime.datetime object)
        ``object_list``
            List of objects published in the given month

``archive_day``
    Daily archive. Requires that ``year``, ``month``, and ``day`` arguments be
    given.

    As in ``archive_month``, you can pass an optional ``month_format``. You can
    also pass ``day_format``, which defaults to ``"%d"`` (day of the month as a
    decimal number, 1-31).

    Uses the template ``app_label/module_name_archive_day`` by default.

    Has the following template context:

        ``object_list``
            List of objects published this day
        ``day``
            The given day (a datetime.datetime object)
        ``previous_day``
            The previous day (a datetime.datetime object)
        ``next_day``
            The next day (a datetime.datetime object), or None if the given
            day is today

``archive_today``
    List of objects for today. Exactly the same as ``archive_day``, except
    the year/month/day arguments are not given, and today's date is used
    instead.

``object_detail``
    Individual object page. Requires ``year``/``month``/``day`` arguments like
    ``archive_day``. This function can be used with two types of URLs: either
    ``/year/month/day/slug/`` or ``/year/month/day/object_id/``.

    If you're using the slug-style URLs, you'll need to have a ``slug`` item in
    your URLconf, and you'll need to pass a ``slug_field`` key in your info
    dictionary to indicate the name of the slug field.

    If your using the object_id-style URLs, you'll just need to give the URL
    pattern an ``object_id`` field.

    You can also pass the ``template_name_field`` argument to indicate that the
    the object stores the name of its template in a field on the object itself.

    As in ``archive_day``, ``object_detail`` takes optional ``month_format``
    and ``day_format`` parameters.

.. _strftime docs: http://www.python.org/doc/current/lib/module-time.html#l2h-1941

Using list/detail generic views
===============================

The list-detail generic-view framework (in the
``django.views.generic.list_detail`` module) is similar to the date-based one,
except the former simply has two views: a list of objects and an individual
object page.

All these views take the same three optional arguments as the date-based ones
-- and, clearly, they don't accept the ``date_field`` argument.

Individual views are:

``object_list``
    List of objects.

    Takes the following optional arguments:

        =======================  =================================================
        Argument                 Description
        =======================  =================================================
        ``paginate_by``          If set to an integer, the view will paginate
                                 objects with ``paginate_by`` objects per page.
                                 The view will expect a ``page`` GET param with
                                 the (zero-indexed) page number.

        ``allow_empty``          If ``False`` and there are no objects to display,
                                 the view will raise a 404 instead of displaying
                                 an empty index page. ``False`` is default.
        =======================  =================================================

    Uses the template ``app_label/module_name_list`` by default.

    Has the following template context:

        ``object_list``
            List of objects
        ``is_paginated``
            Are the results paginated? Either True or False

    If the results are paginated, the context will have some extra variables:

        ``results_per_page``
            Number of objects per page
        ``has_next``
            Is there a next page?
        ``has_previous``
            Is there a previous page?
        ``page``
            The current page number
        ``next``
            The next page number
        ``previous``
            The previous page
        ``pages``
            Number of pages total
        ``hits``
            Total number of objects

``object_detail``
    Object detail page. This works like and takes the same arguments as
    the date-based ``object_detail`` above, except this one, obviously,
    does not take the year/month/day arguments.

Using create/update/delete generic views
========================================

The ``django.views.generic.create_update`` module contains a set of functions
for creating, editing and deleting objects. These views take the same global
arguments as the above sets of generic views. They also have a
``login_required`` argument which, if ``True``, requires the user to be logged
in to have access to the page. (``login_required`` defaults to ``False``.)

The create/update/delete views are:

``create_object``
    Create a new object. Has an extra optional argument, ``post_save_redirect``,
    which is a URL to which the view will redirect after saving the object.
    It defaults to ``object.get_absolute_url()``.

    ``post_save_redirect`` may contain dictionary string formatting, which will
    be interpolated against the object's field attributes. For example, you
    could use ``post_save_redirect="/polls/%(slug)s/"``.

    Uses the template ``app_label/module_name_form`` by default. This is the
    same template as the ``update_object`` view below. Your template can tell
    the different by the presence or absence of ``{{ object }}`` in the
    context.

    Has the following template context:

        form
            The form wrapper for the object

    .. admonition:: Note

        See the `manipulator and formfield documentation`_ for more information
        about using form wrappers in templates.

.. _`manipulator and formfield documentation`: http://www.djangoproject.com/documentation/forms/

``update_object``
    Edit an existing object. Has the same extra slug/ID parameters as
    ``list_detail.object_detail`` does (see above), and the same
    ``post_save_redirect`` as ``create_object`` does.

    Uses the template ``app_label/module_name_form`` by default.

    Has the following template context:

        form
            The form wrapper for the object
        object
            The original object being edited

``delete_object``
    Delete an existing object. The given object will only actually be deleted
    if the request method is POST. If this view is fetched with GET, it will
    display a confirmation page that should contain a form that POSTs to the
    same URL.

    You must provide the ``post_delete_redirect`` argument to this function, so
    that the view knows where to go after the object is deleted.

    If fetched with GET, it uses the template
    ``app_label/module_name_confirm_delete`` by default. It uses no template
    if POSTed -- it simply deletes the object and redirects.

    Has the following template context:

        object
            The object about to be deleted