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

.. module:: django.shortcuts
   :synopsis:
       Convenience shortcuts that span 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()``
============

.. function:: render(request, template_name, context=None, content_type=None, status=None, using=None)

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

   Django does not provide a shortcut function which returns a
   :class:`~django.template.response.TemplateResponse` because the constructor
   of :class:`~django.template.response.TemplateResponse` offers the same level
   of convenience as :func:`render`.

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

``request``
    The request object used to generate this response.

``template_name``
    The full name of a template to use or sequence of template names. If a
    sequence is given, the first template that exists will be used. See the
    :ref:`template loading documentation <template-loading>` for more
    information on how templates are found.

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

``context``
    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.

``content_type``
    The MIME type to use for the resulting document. Defaults to
    ``'text/html'``.

``status``
    The status code for the response. Defaults to ``200``.

``using``
    The :setting:`NAME <TEMPLATES-NAME>` of a template engine to use for
    loading the template.

Example
-------

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

    from django.shortcuts import render


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

This example is equivalent to::

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


    def my_view(request):
        # View code here...
        t = loader.get_template("myapp/index.html")
        c = {"foo": "bar"}
        return HttpResponse(t.render(c, request), content_type="application/xhtml+xml")

``redirect()``
==============

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

   Returns an :class:`~django.http.HttpResponseRedirect` to the appropriate URL
   for the arguments passed.

   The arguments could be:

   * A model: the model's :meth:`~django.db.models.Model.get_absolute_url`
     function will be called.

   * A view name, possibly with arguments: :func:`~django.urls.reverse` will be
     used to reverse-resolve the name.

   * An absolute or relative URL, which will be used as-is for the redirect
     location.

   By default, a temporary redirect is issued with a 302 status code. If
   ``permanent=True``, a permanent redirect is issued with a 301 status code.

   If ``preserve_request=True``, the response instructs the user agent to
   preserve the method and body of the original request when issuing the
   redirect. In this case, temporary redirects use a 307 status code, and
   permanent redirects use a 308 status code. This is better illustrated in the
   following table:

   =========  ================ ================
   permanent  preserve_request HTTP status code
   =========  ================ ================
   ``True``   ``False``        301
   ``False``  ``False``        302
   ``False``  ``True``         307
   ``True``   ``True``         308
   =========  ================ ================

Examples
--------

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

#. 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::

        from django.shortcuts import redirect


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

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

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

#. 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("https://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):
        ...
        obj = MyModel.objects.get(...)
        return redirect(obj, permanent=True)

Additionally, the ``preserve_request`` argument can be used to preserve the
original HTTP method::

    def my_view(request):
        # ...
        obj = MyModel.objects.get(...)
        if request.method in ("POST", "PUT"):
            # Redirection preserves the original request method.
            return redirect(obj, preserve_request=True)
        # ...

``resolve_url()``
=================

.. function:: resolve_url(to, *args, **kwargs)

   Returns a URL string by resolving and normalizing the given ``to`` argument
   into a concrete URL. The parameter ``to`` may be:

   * An object implementing :meth:`~django.db.models.Model.get_absolute_url`,
     in which case the method will be called and its result returned.

   * A view name, view function, or view class, possibly with arguments passed
     as ``*args`` and ``**kwargs``, in which case :func:`~django.urls.reverse`
     will be used to reverse-resolve the view.

   * A URL string, which will be returned unchanged.

   This function is used internally by the :func:`redirect` shortcut to
   determine the target URL for the redirect location.

Examples
--------

#. Resolving a URL for a model that defines
   :meth:`~django.db.models.Model.get_absolute_url`:

   .. code-block:: python
       :caption: ``models.py``

       from django.db import models
       from django.urls import reverse


       class Article(models.Model):
           title = models.CharField(max_length=100)

           def get_absolute_url(self):
               return reverse("article-detail", args=[self.pk])


   .. code-block:: python
       :caption: ``views.py``

       from django.http import JsonResponse
       from django.shortcuts import get_object_or_404, resolve_url
       from .models import Article


       def article_api_view(request, pk):
           """Return metadata about an article, including its canonical URL."""
           article = get_object_or_404(Article, pk=pk)
           return JsonResponse(
               {
                   "id": article.pk,
                   "title": article.title,
                   "url": resolve_url(article),
               }
           )

#. Resolving a target URL for use outside of a redirect, such as in an HTTP
   response header::

    from django.conf import settings
    from django.http import HttpResponse
    from django.shortcuts import resolve_url


    def login_success(request):
        response = HttpResponse("Login successful")
        response["X-Next-URL"] = resolve_url(settings.LOGIN_REDIRECT_URL)
        return response

``get_object_or_404()``
=======================

.. function:: get_object_or_404(klass, *args, **kwargs)
.. function:: aget_object_or_404(klass, *args, **kwargs)

    *Asynchronous version*: ``aget_object_or_404()``

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

Arguments
---------

``klass``
    A :class:`~django.db.models.Model` class,
    a :class:`~django.db.models.Manager`,
    or a :class:`~django.db.models.query.QuerySet` instance from which to get
    the object.

``*args``
    :ref:`q-objects`.

``**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):
        obj = get_object_or_404(MyModel, pk=1)

This example is equivalent to::

    from django.http import Http404


    def my_view(request):
        try:
            obj = MyModel.objects.get(pk=1)
        except MyModel.DoesNotExist:
            raise Http404("No MyModel matches the given query.")

The most common use case is to pass a :class:`~django.db.models.Model`, as
shown above. However, you can also pass a
:class:`~django.db.models.query.QuerySet` instance::

    queryset = Book.objects.filter(title__startswith="M")
    get_object_or_404(queryset, pk=1)

The above example is a bit contrived since it's equivalent to doing::

    get_object_or_404(Book, title__startswith="M", pk=1)

but it can be useful if you are passed the ``queryset`` variable from somewhere
else.

Finally, you can also use a :class:`~django.db.models.Manager`. This is useful
for example if you have a
:ref:`custom manager<custom-managers>`::

    get_object_or_404(Book.dahl_objects, title="Matilda")

You can also use
:class:`related managers<django.db.models.fields.related.RelatedManager>`::

    author = Author.objects.get(name="Roald Dahl")
    get_object_or_404(author.book_set, title="Matilda")

Note: As with ``get()``, a
:class:`~django.core.exceptions.MultipleObjectsReturned` exception
will be raised if more than one object is found.

``get_list_or_404()``
=====================

.. function:: get_list_or_404(klass, *args, **kwargs)
.. function:: aget_list_or_404(klass, *args, **kwargs)

    *Asynchronous version*: ``aget_list_or_404()``

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

Arguments
---------

``klass``
    A :class:`~django.db.models.Model`, :class:`~django.db.models.Manager` or
    :class:`~django.db.models.query.QuerySet` instance from which to get the
    list.

``*args``
    :ref:`q-objects`.

``**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("No MyModel matches the given query.")

