mixins-date-based.txt

=================
Date-based mixins
=================

.. currentmodule:: django.views.generic.dates

.. note::

    All the date formatting attributes in these mixins use
    :func:`~time.strftime` format characters. Do not try to use the format
    characters from the :ttag:`now` template tag as they are not compatible.

``YearMixin``
=============

.. class:: YearMixin

    A mixin that can be used to retrieve and provide parsing information for a
    year component of a date.

    **Methods and Attributes**

    .. attribute:: year_format

        The :func:`~time.strftime` format to use when parsing the year.
        By default, this is ``'%Y'``.

    .. attribute:: year

        **Optional** The value for the year, as a string. By default, set to
        ``None``, which means the year will be determined using other means.

    .. method:: get_year_format()

        Returns the :func:`~time.strftime` format to use when parsing the
        year. Returns :attr:`~YearMixin.year_format` by default.

    .. method:: get_year()

        Returns the year for which this view will display data, as a string.
        Tries the following sources, in order:

        * The value of the :attr:`YearMixin.year` attribute.
        * The value of the ``year`` argument captured in the URL pattern.
        * The value of the ``year`` ``GET`` query argument.

        Raises a 404 if no valid year specification can be found.

    .. method:: get_next_year(date)

        Returns a date object containing the first day of the year after the
        date provided. This function can also return ``None`` or raise an
        :class:`~django.http.Http404` exception, depending on the values of
        :attr:`~BaseDateListView.allow_empty` and
        :attr:`~DateMixin.allow_future`.

    .. method:: get_previous_year(date)

        Returns a date object containing the first day of the year before the
        date provided. This function can also return ``None`` or raise an
        :class:`~django.http.Http404` exception, depending on the values of
        :attr:`~BaseDateListView.allow_empty` and
        :attr:`~DateMixin.allow_future`.

``MonthMixin``
==============

.. class:: MonthMixin

    A mixin that can be used to retrieve and provide parsing information for a
    month component of a date.

    **Methods and Attributes**

    .. attribute:: month_format

        The :func:`~time.strftime` format to use when parsing the month. By
        default, this is ``'%b'``.

    .. attribute:: month

        **Optional** The value for the month, as a string. By default, set to
        ``None``, which means the month will be determined using other means.

    .. method:: get_month_format()

        Returns the :func:`~time.strftime` format to use when parsing the
        month. Returns :attr:`~MonthMixin.month_format` by default.

    .. method:: get_month()

        Returns the month for which this view will display data, as a string.
        Tries the following sources, in order:

        * The value of the :attr:`MonthMixin.month` attribute.
        * The value of the ``month`` argument captured in the URL pattern.
        * The value of the ``month`` ``GET`` query argument.

        Raises a 404 if no valid month specification can be found.

    .. method:: get_next_month(date)

        Returns a date object containing the first day of the month after the
        date provided. This function can also return ``None`` or raise an
        :class:`~django.http.Http404` exception, depending on the values of
        :attr:`~BaseDateListView.allow_empty` and
        :attr:`~DateMixin.allow_future`.

    .. method:: get_previous_month(date)

        Returns a date object containing the first day of the month before the
        date provided. This function can also return ``None`` or raise an
        :class:`~django.http.Http404` exception, depending on the values of
        :attr:`~BaseDateListView.allow_empty` and
        :attr:`~DateMixin.allow_future`.

``DayMixin``
============

.. class:: DayMixin

    A mixin that can be used to retrieve and provide parsing information for a
    day component of a date.

    **Methods and Attributes**

    .. attribute:: day_format

        The :func:`~time.strftime` format to use when parsing the day. By
        default, this is ``'%d'``.

    .. attribute:: day

        **Optional** The value for the day, as a string. By default, set to
        ``None``, which means the day will be determined using other means.

    .. method:: get_day_format()

        Returns the :func:`~time.strftime` format to use when parsing the day.
        Returns :attr:`~DayMixin.day_format` by default.

    .. method:: get_day()

        Returns the day for which this view will display data, as a string.
        Tries the following sources, in order:

        * The value of the :attr:`DayMixin.day` attribute.
        * The value of the ``day`` argument captured in the URL pattern.
        * The value of the ``day`` ``GET`` query argument.

        Raises a 404 if no valid day specification can be found.

    .. method:: get_next_day(date)

        Returns a date object containing the next valid day after the date
        provided. This function can also return ``None`` or raise an
        :class:`~django.http.Http404` exception, depending on the values of
        :attr:`~BaseDateListView.allow_empty` and
        :attr:`~DateMixin.allow_future`.

    .. method:: get_previous_day(date)

        Returns a date object containing the previous valid day. This function
        can also return ``None`` or raise an :class:`~django.http.Http404`
        exception, depending on the values of
        :attr:`~BaseDateListView.allow_empty` and
        :attr:`~DateMixin.allow_future`.

``WeekMixin``
=============

.. class:: WeekMixin

    A mixin that can be used to retrieve and provide parsing information for a
    week component of a date.

    **Methods and Attributes**

    .. attribute:: week_format

        The :func:`~time.strftime` format to use when parsing the week. By
        default, this is ``'%U'``, which means the week starts on Sunday. Set
        it to ``'%W'`` or ``'%V'`` (ISO 8601 week) if your week starts on
        Monday.

        .. versionadded:: 3.2

            Support for the ``'%V'`` week format was added.

    .. attribute:: week

        **Optional** The value for the week, as a string. By default, set to
        ``None``, which means the week will be determined using other means.

    .. method:: get_week_format()

        Returns the :func:`~time.strftime` format to use when parsing the
        week. Returns :attr:`~WeekMixin.week_format` by default.

    .. method:: get_week()

        Returns the week for which this view will display data, as a string.
        Tries the following sources, in order:

        * The value of the :attr:`WeekMixin.week` attribute.
        * The value of the ``week`` argument captured in the URL pattern
        * The value of the ``week`` ``GET`` query argument.

        Raises a 404 if no valid week specification can be found.

    .. method:: get_next_week(date)

        Returns a date object containing the first day of the week after the
        date provided. This function can also return ``None`` or raise an
        :class:`~django.http.Http404` exception, depending on the values of
        :attr:`~BaseDateListView.allow_empty` and
        :attr:`~DateMixin.allow_future`.

    .. method:: get_prev_week(date)

        Returns a date object containing the first day of the week before the
        date provided. This function can also return ``None`` or raise an
        :class:`~django.http.Http404` exception, depending on the values of
        :attr:`~BaseDateListView.allow_empty` and
        :attr:`~DateMixin.allow_future`.

``DateMixin``
=============

.. class:: DateMixin

    A mixin class providing common behavior for all date-based views.

    **Methods and Attributes**

    .. attribute:: date_field

        The name of the ``DateField`` or ``DateTimeField`` in the
        ``QuerySet``’s model that the date-based archive should use to
        determine the list of objects to display on the page.

        When :doc:`time zone support </topics/i18n/timezones>` is enabled and
        ``date_field`` is a ``DateTimeField``, dates are assumed to be in the
        current time zone. Otherwise, the queryset could include objects from
        the previous or the next day in the end user's time zone.

        .. warning::

            In this situation, if you have implemented per-user time zone
            selection, the same URL may show a different set of objects,
            depending on the end user's time zone. To avoid this, you should
            use a ``DateField`` as the ``date_field`` attribute.

    .. attribute:: allow_future

        A boolean specifying whether to include "future" objects on this page,
        where "future" means objects in which the field specified in
        ``date_field`` is greater than the current date/time. By default, this
        is ``False``.

    .. method:: get_date_field()

        Returns the name of the field that contains the date data that this
        view will operate on. Returns :attr:`~DateMixin.date_field` by default.

    .. method:: get_allow_future()

        Determine whether to include "future" objects on this page, where
        "future" means objects in which the field specified in ``date_field``
        is greater than the current date/time. Returns
        :attr:`~DateMixin.allow_future` by default.

``BaseDateListView``
====================

.. class:: BaseDateListView

    A base class that provides common behavior for all date-based views. There
    won't normally be a reason to instantiate
    :class:`~django.views.generic.dates.BaseDateListView`; instantiate one of
    the subclasses instead.

    While this view (and its subclasses) are executing, ``self.object_list``
    will contain the list of objects that the view is operating upon, and
    ``self.date_list`` will contain the list of dates for which data is
    available.

    **Mixins**

    * :class:`~django.views.generic.dates.DateMixin`
    * :class:`~django.views.generic.list.MultipleObjectMixin`

    **Methods and Attributes**

    .. attribute:: allow_empty

        A boolean specifying whether to display the page if no objects are
        available. If this is ``True`` and no objects are available, the view
        will display an empty page instead of raising a 404.

        This is identical to
        :attr:`django.views.generic.list.MultipleObjectMixin.allow_empty`,
        except for the default value, which is ``False``.

    .. attribute:: date_list_period

        **Optional** A string defining the aggregation period for
        ``date_list``. It must be one of ``'year'`` (default), ``'month'``, or
        ``'day'``.

    .. method:: get_dated_items()

        Returns a 3-tuple containing (``date_list``, ``object_list``,
        ``extra_context``).

        ``date_list`` is the list of dates for which data is available.
        ``object_list`` is the list of objects. ``extra_context`` is a
        dictionary of context data that will be added to any context data
        provided by the
        :class:`~django.views.generic.list.MultipleObjectMixin`.

    .. method:: get_dated_queryset(**lookup)

        Returns a queryset, filtered using the query arguments defined by
        ``lookup``. Enforces any restrictions on the queryset, such as
        ``allow_empty`` and ``allow_future``.

    .. method:: get_date_list_period()

        Returns the aggregation period for ``date_list``. Returns
        :attr:`~BaseDateListView.date_list_period` by default.

    .. method:: get_date_list(queryset, date_type=None, ordering='ASC')

        Returns the list of dates of type ``date_type`` for which ``queryset``
        contains entries. For example, ``get_date_list(qs, 'year')`` will
        return the list of years for which ``qs`` has entries. If
        ``date_type`` isn't provided, the result of
        :meth:`~BaseDateListView.get_date_list_period` is used. ``date_type``
        and ``ordering`` are passed to
        :meth:`QuerySet.dates()<django.db.models.query.QuerySet.dates>`.