django/docs/ref/class-based-views/mixins-multiple-object.txt

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======================
Multiple object mixins
======================
MultipleObjectMixin
-------------------
.. class:: django.views.generic.list.MultipleObjectMixin
A mixin that can be used to display a list of objects.
If ``paginate_by`` is specified, Django will paginate the results returned
by this. You can specify the page number in the URL in one of two ways:
* Use the ``page`` parameter in the URLconf. For example, this is what
your URLconf might look like::
url(r'^objects/page(?P<page>[0-9]+)/$', PaginatedView.as_view()),
* Pass the page number via the ``page`` query-string parameter. For
example, a URL would look like this::
/objects/?page=3
These values and lists are 1-based, not 0-based, so the first page would be
represented as page ``1``.
For more on pagination, read the :doc:`pagination documentation
</topics/pagination>`.
As a special case, you are also permitted to use ``last`` as a value for
``page``::
/objects/?page=last
This allows you to access the final page of results without first having to
determine how many pages there are.
Note that ``page`` *must* be either a valid page number or the value
``last``; any other value for ``page`` will result in a 404 error.
**Extends**
* :class:`django.views.generic.base.ContextMixin`
**Methods and Attributes**
.. attribute:: allow_empty
A boolean specifying whether to display the page if no objects are
available. If this is ``False`` and no objects are available, the view
will raise a 404 instead of displaying an empty page. By default, this
is ``True``.
.. attribute:: model
The model that this view will display data for. Specifying ``model
= Foo`` is effectively the same as specifying ``queryset =
Foo.objects.all()``, where ``objects`` stands for ``Foo``s
:ref:`default manager <default-managers>`.
.. attribute:: queryset
A ``QuerySet`` that represents the objects. If provided, the value of
``queryset`` supersedes the value provided for :attr:`model`.
.. warning::
``queryset`` is a class attribute with a *mutable* value so care
must be taken when using it directly. Before using it, either call
its :meth:`~django.db.models.query.QuerySet.all` method or
retrieve it with :meth:`get_queryset` which takes care of the
cloning behind the scenes.
.. attribute:: ordering
.. versionadded:: 1.8
A string or list of strings specifying the ordering to apply to the ``queryset``.
Valid values are the same as those for :meth:`~django.db.models.query.QuerySet.order_by`.
.. attribute:: paginate_by
An integer specifying how many objects should be displayed per page. If
this is given, the view will paginate objects with
``paginate_by`` objects per page. The view will
expect either a ``page`` query string parameter (via ``request.GET``)
or a ``page`` variable specified in the URLconf.
.. attribute:: paginate_orphans
An integer specifying the number of "overflow" objects the last page
can contain. This extends the :attr:`paginate_by` limit on the last
page by up to ``paginate_orphans``, in order to keep the last page from
having a very small number of objects.
.. attribute:: page_kwarg
A string specifying the name to use for the page parameter.
The view will expect this parameter to be available either as a query
string parameter (via ``request.GET``) or as a kwarg variable specified
in the URLconf. Defaults to ``page``.
.. attribute:: paginator_class
The paginator class to be used for pagination. By default,
:class:`django.core.paginator.Paginator` is used. If the custom paginator
class doesn't have the same constructor interface as
:class:`django.core.paginator.Paginator`, you will also need to
provide an implementation for :meth:`get_paginator`.
.. attribute:: context_object_name
Designates the name of the variable to use in the context.
.. method:: get_queryset()
Get the list of items for this view. This must be an iterable and may
be a queryset (in which queryset-specific behavior will be enabled).
.. method:: get_ordering()
.. versionadded:: 1.8
Returns a string (or iterable of strings) that defines the ordering that
will be applied to the ``queryset``.
Returns :attr:`ordering` by default.
.. method:: paginate_queryset(queryset, page_size)
Returns a 4-tuple containing (``paginator``, ``page``, ``object_list``,
``is_paginated``).
Constructed by paginating ``queryset`` into pages of size ``page_size``.
If the request contains a ``page`` argument, either as a captured URL
argument or as a GET argument, ``object_list`` will correspond to the
objects from that page.
.. method:: get_paginate_by(queryset)
Returns the number of items to paginate by, or ``None`` for no
pagination. By default this simply returns the value of
:attr:`paginate_by`.
.. method:: get_paginator(queryset, per_page, orphans=0, allow_empty_first_page=True)
Returns an instance of the paginator to use for this view. By default,
instantiates an instance of :attr:`paginator_class`.
.. method:: get_paginate_orphans()
An integer specifying the number of "overflow" objects the last page
can contain. By default this simply returns the value of
:attr:`paginate_orphans`.
.. method:: get_allow_empty()
Return a boolean specifying whether to display the page if no objects
are available. If this method returns ``False`` and no objects are
available, the view will raise a 404 instead of displaying an empty
page. By default, this is ``True``.
.. method:: get_context_object_name(object_list)
Return the context variable name that will be used to contain
the list of data that this view is manipulating. If
``object_list`` is a queryset of Django objects and
:attr:`context_object_name` is not set,
the context name will be the ``model_name`` of the model that
the queryset is composed from, with postfix ``'_list'``
appended. For example, the model ``Article`` would have a
context object named ``article_list``.
.. method:: get_context_data(**kwargs)
Returns context data for displaying the list of objects.
**Context**
* ``object_list``: The list of objects that this view is displaying. If
``context_object_name`` is specified, that variable will also be set
in the context, with the same value as ``object_list``.
* ``is_paginated``: A boolean representing whether the results are
paginated. Specifically, this is set to ``False`` if no page size has
been specified, or if the available objects do not span multiple
pages.
* ``paginator``: An instance of
:class:`django.core.paginator.Paginator`. If the page is not
paginated, this context variable will be ``None``.
* ``page_obj``: An instance of
:class:`django.core.paginator.Page`. If the page is not paginated,
this context variable will be ``None``.
MultipleObjectTemplateResponseMixin
-----------------------------------
.. class:: django.views.generic.list.MultipleObjectTemplateResponseMixin
A mixin class that performs template-based response rendering for views
that operate upon a list of object instances. Requires that the view it is
mixed with provides ``self.object_list``, the list of object instances that
the view is operating on. ``self.object_list`` may be, but is not required
to be, a :class:`~django.db.models.query.QuerySet`.
**Extends**
* :class:`~django.views.generic.base.TemplateResponseMixin`
**Methods and Attributes**
.. attribute:: template_name_suffix
The suffix to append to the auto-generated candidate template name.
Default suffix is ``_list``.
.. method:: get_template_names()
Returns a list of candidate template names. Returns the following list:
* the value of ``template_name`` on the view (if provided)
* ``<app_label>/<model_name><template_name_suffix>.html``