Ticket #14150: shortcuts.txt

.. _topics-http-shortcuts:

=========================
Django shortcut functions
=========================

.. module:: django.shortcuts
   :synopsis:
       Convience shortcuts that spam multiple levels of Django's MVC stack.

.. index:: shortcuts

The package ``django.shortcuts`` collects helper functions and classes that
"span" multiple levels of MVC. In other words, these functions/classes
introduce controlled coupling for convenience's sake.

``render_to_response``
======================

.. function:: render_to_response(template[, dictionary][, context_instance][, mimetype])

   Renders a given template with a given context dictionary and returns an
   :class:`~django.http.HttpResponse` object with that rendered text.

Required arguments
------------------

``template``
    The full name of a template to use or sequence of template names.

Optional arguments
------------------

``dictionary``
    A dictionary of values to add to the template context. By default, this
    is an empty dictionary. If a value in the dictionary is callable, the
    view will call it just before rendering the template.

``context_instance``
    The context instance to render the template with. By default, the template
    will be rendered with a ``Context`` instance (filled with values from
    ``dictionary``). If you need to use :ref:`context processors
    <subclassing-context-requestcontext>`, render the template with a
    ``RequestContext`` instance instead. Your code might look something like
    this::

        return render_to_response('my_template.html',
                                  my_data_dictionary,
                                  context_instance=RequestContext(request))

``mimetype``

    .. versionadded:: 1.0

    The MIME type to use for the resulting document. Defaults to the value of
    the :setting:`DEFAULT_CONTENT_TYPE` setting.

Example
-------

The following example renders the template ``myapp/index.html`` with the
MIME type ``application/xhtml+xml``::

    from django.shortcuts import render_to_response

    def my_view(request):
        # View code here...
        return render_to_response('myapp/index.html', {"foo": "bar"},
            mimetype="application/xhtml+xml")

This example is equivalent to::

    from django.http import HttpResponse
    from django.template import Context, loader

    def my_view(request):
        # View code here...
        t = loader.get_template('myapp/template.html')
        c = Context({'foo': 'bar'})
        return HttpResponse(t.render(c),
            mimetype="application/xhtml+xml")

``redirect``
============

.. function:: redirect(to[, permanent=False], *args, **kwargs)

   .. versionadded:: 1.1

   Returns an HttpResponseRedirect to the apropriate URL for the arguments
   passed.

   The arguments could be:

       * A model: the model's `get_absolute_url()` function will be called.

       * A view name, possibly with arguments: `urlresolvers.reverse()` will
         be used to reverse-resolve the name.

       * A URL, which will be used as-is for the redirect location.

   By default issues a temporary redirect; pass permanent=True to issue a
   permanent redirect

Examples
--------

You can use the :func:`redirect` function in a number of ways.

    1. By passing some object; that object's
       :meth:`~django.db.models.Model.get_absolute_url` method will be called
       to figure out the redirect URL::

            def my_view(request):
                ...
                object = MyModel.objects.get(...)
                return redirect(object)

    2. By passing the name of a view and optionally some positional or
       keyword arguments; the URL will be reverse resolved using the
       :func:`~django.core.urlresolvers.reverse` method::

            def my_view(request):
                ...
                return redirect('some-view-name', foo='bar')

    3. By passing a hardcoded URL to redirect to::

            def my_view(request):
                ...
                return redirect('/some/url/')

       This also works with full URLs::

            def my_view(request):
                ...
                return redirect('http://example.com/')

By default, :func:`redirect` returns a temporary redirect. All of the above
forms accept a ``permanent`` argument; if set to ``True`` a permanent redirect
will be returned::

    def my_view(request):
        ...
        object = MyModel.objects.get(...)
        return redirect(object, permanent=True)

``get_object_or_404``
=====================

.. function:: get_object_or_404(klass, *args, **kwargs)

   Calls :meth:`~django.db.models.QuerySet.get()` on a given model manager,
   but it raises ``django.http.Http404`` instead of the model's
   ``DoesNotExist`` exception.

Required arguments
------------------

``klass``
    A ``Model``, ``Manager`` or ``QuerySet`` instance from which to get the
    object.

``**kwargs``
    Lookup parameters, which should be in the format accepted by ``get()`` and
    ``filter()``.

Example
-------

The following example gets the object with the primary key of 1 from
``MyModel``::

    from django.shortcuts import get_object_or_404

    def my_view(request):
        my_object = get_object_or_404(MyModel, pk=1)

This example is equivalent to::

    from django.http import Http404

    def my_view(request):
        try:
            my_object = MyModel.objects.get(pk=1)
        except MyModel.DoesNotExist:
            raise Http404

Note: As with ``get()``, an ``MultipleObjectsReturned`` exception will be
raised if more than one object is found.

``get_objects_or_404``
===================

.. function:: get_objects_or_404(klass, *args, **kwargs)

   Returns the result of :meth:`~django.db.models.QuerySet.filter()` on a
   given model manager, raising ``django.http.Http404`` if no objects matched.

Required arguments
------------------

``klass``
    A ``Model``, ``Manager`` or ``QuerySet`` instance from which to get the
    object.

``**kwargs``
    Lookup parameters, which should be in the format accepted by ``get()`` and
    ``filter()``.

Example
-------

The following example gets all published objects from ``MyModel``::

    from django.shortcuts import get_objects_or_404

    def my_view(request):
        my_objects = get_objects_or_404(MyModel, published=True)

This example is equivalent to::

    from django.http import Http404

    def my_view(request):
        my_objects = MyModel.objects.filter(published=True)
        if not my_objects:
            raise Http404

Because get_objects_or_404 returns a queryset, it's possible to continue
editing it:

    from django.shortcuts import get_objects_or_404

    def my_view(request):
        my_objects = get_objects_or_404(MyModel, published=True).order_by('pub_date')

``get_list_or_404``
===================

.. function:: get_list_or_404(klass, *args, **kwargs)

   Returns the result of :meth:`~django.db.models.QuerySet.filter()` on a
   given model manager, raising ``django.http.Http404`` if the resulting list
   is empty.

Required arguments
------------------

``klass``
    A ``Model``, ``Manager`` or ``QuerySet`` instance from which to get the
    object.

``**kwargs``
    Lookup parameters, which should be in the format accepted by ``get()`` and
    ``filter()``.

Example
-------

The following example gets all published objects from ``MyModel``::

    from django.shortcuts import get_list_or_404

    def my_view(request):
        my_objects = get_list_or_404(MyModel, published=True)

This example is equivalent to::

    from django.http import Http404

    def my_view(request):
        my_objects = list(MyModel.objects.filter(published=True))
        if not my_objects:
            raise Http404