===================
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 Python code.

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 *
    from django_website.apps.blog.models import Entry

    info_dict = {
        'model': Entry,
        '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``. ``'model'``
tells the generic view which model to use (``Entry``, 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
``model``, ``date_field``, etc.).

Most generic views require the ``model`` key, which is your model class (*not*
an instance of the class).

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 ``model``, all
date-based generic views require the ``date_field`` argument. 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.

    ``processors``           A tuple of processors to apply to the
                             ``RequestContext`` of this view's template. See the
                             `RequestContext docs`_
    =======================  ==================================================

.. _database API docs: http://www.djangoproject.com/documentation/db_api/
.. _RequestContext docs: http://www.djangoproject.com/documentation/templates_python/#subclassing-context-djangocontext

The date-based generic functions are:

``archive_index``
    A top-level index page showing the "latest" objects.

    Takes the following optional arguments:

        =======================  =================================================
        Argument                 Description
        =======================  =================================================
        ``num_latest``           The number of items to display on the page.
                                 Defaults to 15.

        ``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>/<model_name>_archive.html`` by default, where:

        * ``<model_name>`` is your model's name in all lowercase. For a model
          ``StaffMember``, that'd be ``staffmember``.

        * ``<app_label>`` is the right-most part of the full Python path to
          your model's app. For example, if your model lives in
          ``apps/blog/models.py``, that'd be ``blog``.

    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.

    Takes an optional ``allow_empty`` parameter, as ``archive_index``.

    Uses the template ``<app_label>/<model_name>_archive_year.html`` 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"``.

    Takes an optional ``allow_empty`` parameter, as ``archive_index``.

    **New in Django development version:** Takes an optional
    ``template_object_name`` parameter, which designates the name of the
    template variable to use. Default is ``'object'``.

    Uses the template ``<app_label>/<model_name>_archive_month.html`` by default.

    Has the following template context:

        ``month``
            The given month (a datetime.date object)
        ``next_month``
            **New in Django development version.** The first day of the next
            month, or None if the next month is in the future (a datetime.date
            object)
        ``previous_month``
            **New in Django development version.** The first day of the
            previous month (a datetime.date object)
        ``object_list``
            List of objects published in the given month.
            In the Django development version, you can change this variable
            name from ``object_list`` by using the ``template_object_name``
            parameter. (See above.) For example, if ``template_object_name`` is
            ``foo``, the variable will be ``foo_list``.

``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).

    **New in Django development version:** Takes an optional
    ``template_object_name`` parameter, which designates the name of the
    template variable to use. Default is ``'object'``.

    Uses the template ``<app_label>/<model_name>_archive_day.html`` by default.

    Has the following template context:

        ``object_list``
            List of objects published on the given day.
            In the Django development version, you can change this variable
            name from ``object_list`` by using the ``template_object_name``
            parameter. (See above.) For example, if ``template_object_name`` is
            ``foo``, the variable will be ``foo_list``.
        ``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 you're 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.

    **New in Django development version:** Takes an optional
    ``template_object_name`` parameter, which designates the name of the
    template variable to use. Default is ``'object'``.

.. _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 four 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.

        ``template_object_name``  **New in Django development version.** Designates
                                  the name of the object template variable. Default
                                  is ``'object'``.
        ========================  =================================================

    Uses the template ``<app_label>/<module_name_list>.html`` by default.

    Has the following template context:

        ``object_list``
            List of objects. In the Django development version, you can change
            this variable name from ``object_list`` by using the
            ``template_object_name`` parameter. (See above.) For example, if
            ``template_object_name`` is ``foo``, the variable will be
            ``foo_list``.
        ``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>/<model_name>_form.html`` by default. This
    is the same template as the ``update_object`` view below. Your template can
    tell the difference 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.

    **New in Django development version:** Takes an optional
    ``template_object_name`` parameter, which designates the name of the
    template variable to use. Default is ``'object'``.

    Uses the template ``<app_label>/<model_name>_form.html`` by default.

    Has the following template context:

        form
            The form wrapper for the object
        object
            The original object being edited.
            In the Django development version, you can change this variable
            name from ``object`` by using the ``template_object_name``
            parameter. (See above.) For example, if ``template_object_name`` is
            ``foo``, the variable will be ``foo`` instead of ``object``.

``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>/<model_name>_confirm_delete`` by default. It uses no template
    if POSTed -- it simply deletes the object and redirects.

    **New in Django development version:** Takes an optional
    ``template_object_name`` parameter, which designates the name of the
    template variable to use. Default is ``'object'``.

    Has the following template context:

        object
            The object about to be deleted
            In the Django development version, you can change this variable
            name from ``object`` by using the ``template_object_name``
            parameter. (See above.) For example, if ``template_object_name`` is
            ``foo``, the variable will be ``foo`` instead of ``object``.
