django1/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::

        path('objects/page<int:page>/', 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

        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()

        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 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 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``