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265 lines
8.6 KiB
Plaintext
265 lines
8.6 KiB
Plaintext
=================================
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``django.urls`` utility functions
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=================================
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.. module:: django.urls
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``reverse()``
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=============
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If you need to use something similar to the :ttag:`url` template tag in
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your code, Django provides the following function:
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.. function:: reverse(viewname, urlconf=None, args=None, kwargs=None, current_app=None)
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``viewname`` can be a :ref:`URL pattern name <naming-url-patterns>` or the
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callable view object used in the URLconf. For example, given the following
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``url``::
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from news import views
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path("archive/", views.archive, name="news-archive")
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you can use any of the following to reverse the URL::
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# using the named URL
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reverse("news-archive")
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# passing a callable object
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# (This is discouraged because you can't reverse namespaced views this way.)
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from news import views
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reverse(views.archive)
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If the URL accepts arguments, you may pass them in ``args``. For example::
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from django.urls import reverse
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def myview(request):
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return HttpResponseRedirect(reverse("arch-summary", args=[1945]))
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You can also pass ``kwargs`` instead of ``args``. For example:
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.. code-block:: pycon
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>>> reverse("admin:app_list", kwargs={"app_label": "auth"})
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'/admin/auth/'
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``args`` and ``kwargs`` cannot be passed to ``reverse()`` at the same time.
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If no match can be made, ``reverse()`` raises a
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:class:`~django.urls.NoReverseMatch` exception.
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The ``reverse()`` function can reverse a large variety of regular expression
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patterns for URLs, but not every possible one. The main restriction at the
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moment is that the pattern cannot contain alternative choices using the
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vertical bar (``"|"``) character. You can quite happily use such patterns for
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matching against incoming URLs and sending them off to views, but you cannot
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reverse such patterns.
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The ``current_app`` argument allows you to provide a hint to the resolver
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indicating the application to which the currently executing view belongs.
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This ``current_app`` argument is used as a hint to resolve application
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namespaces into URLs on specific application instances, according to the
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:ref:`namespaced URL resolution strategy <topics-http-reversing-url-namespaces>`.
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The ``urlconf`` argument is the URLconf module containing the URL patterns to
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use for reversing. By default, the root URLconf for the current thread is used.
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.. note::
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The string returned by ``reverse()`` is already
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:ref:`urlquoted <uri-and-iri-handling>`. For example:
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.. code-block:: pycon
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>>> reverse("cities", args=["Orléans"])
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'.../Orl%C3%A9ans/'
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Applying further encoding (such as :func:`urllib.parse.quote`) to the output
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of ``reverse()`` may produce undesirable results.
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.. admonition:: Reversing class-based views by view object
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The view object can also be the result of calling
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:meth:`~django.views.generic.base.View.as_view` if the same view object is
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used in the URLConf. Following the original example, the view object could
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be defined as:
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.. code-block:: python
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:caption: ``news/views.py``
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from django.views import View
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class ArchiveView(View): ...
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archive = ArchiveView.as_view()
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However, remember that namespaced views cannot be reversed by view object.
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``reverse_lazy()``
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==================
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A lazily evaluated version of `reverse()`_.
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.. function:: reverse_lazy(viewname, urlconf=None, args=None, kwargs=None, current_app=None)
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It is useful for when you need to use a URL reversal before your project's
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URLConf is loaded. Some common cases where this function is necessary are:
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* providing a reversed URL as the ``url`` attribute of a generic class-based
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view.
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* providing a reversed URL to a decorator (such as the ``login_url`` argument
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for the :func:`django.contrib.auth.decorators.permission_required`
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decorator).
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* providing a reversed URL as a default value for a parameter in a function's
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signature.
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``resolve()``
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=============
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The ``resolve()`` function can be used for resolving URL paths to the
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corresponding view functions. It has the following signature:
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.. function:: resolve(path, urlconf=None)
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``path`` is the URL path you want to resolve. As with
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:func:`~django.urls.reverse`, you don't need to worry about the ``urlconf``
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parameter. The function returns a :class:`ResolverMatch` object that allows you
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to access various metadata about the resolved URL.
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If the URL does not resolve, the function raises a
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:exc:`~django.urls.Resolver404` exception (a subclass of
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:class:`~django.http.Http404`) .
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.. class:: ResolverMatch
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.. attribute:: ResolverMatch.func
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The view function that would be used to serve the URL
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.. attribute:: ResolverMatch.args
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The arguments that would be passed to the view function, as
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parsed from the URL.
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.. attribute:: ResolverMatch.kwargs
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All keyword arguments that would be passed to the view function, i.e.
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:attr:`~ResolverMatch.captured_kwargs` and
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:attr:`~ResolverMatch.extra_kwargs`.
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.. attribute:: ResolverMatch.captured_kwargs
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The captured keyword arguments that would be passed to the view
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function, as parsed from the URL.
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.. attribute:: ResolverMatch.extra_kwargs
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The additional keyword arguments that would be passed to the view
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function.
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.. attribute:: ResolverMatch.url_name
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The name of the URL pattern that matches the URL.
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.. attribute:: ResolverMatch.route
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The route of the matching URL pattern.
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For example, if ``path('users/<id>/', ...)`` is the matching pattern,
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``route`` will contain ``'users/<id>/'``.
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.. attribute:: ResolverMatch.tried
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The list of URL patterns tried before the URL either matched one or
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exhausted available patterns.
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.. attribute:: ResolverMatch.app_name
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The application namespace for the URL pattern that matches the
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URL.
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.. attribute:: ResolverMatch.app_names
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The list of individual namespace components in the full
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application namespace for the URL pattern that matches the URL.
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For example, if the ``app_name`` is ``'foo:bar'``, then ``app_names``
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will be ``['foo', 'bar']``.
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.. attribute:: ResolverMatch.namespace
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The instance namespace for the URL pattern that matches the
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URL.
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.. attribute:: ResolverMatch.namespaces
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The list of individual namespace components in the full
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instance namespace for the URL pattern that matches the URL.
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i.e., if the namespace is ``foo:bar``, then namespaces will be
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``['foo', 'bar']``.
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.. attribute:: ResolverMatch.view_name
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The name of the view that matches the URL, including the namespace if
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there is one.
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A :class:`ResolverMatch` object can then be interrogated to provide
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information about the URL pattern that matches a URL::
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# Resolve a URL
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match = resolve("/some/path/")
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# Print the URL pattern that matches the URL
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print(match.url_name)
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A :class:`ResolverMatch` object can also be assigned to a triple::
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func, args, kwargs = resolve("/some/path/")
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One possible use of :func:`~django.urls.resolve` would be to test whether a
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view would raise a ``Http404`` error before redirecting to it::
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from urllib.parse import urlsplit
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from django.urls import resolve
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from django.http import Http404, HttpResponseRedirect
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def myview(request):
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next = request.META.get("HTTP_REFERER", None) or "/"
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response = HttpResponseRedirect(next)
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# modify the request and response as required, e.g. change locale
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# and set corresponding locale cookie
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view, args, kwargs = resolve(urlsplit(next).path)
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kwargs["request"] = request
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try:
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view(*args, **kwargs)
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except Http404:
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return HttpResponseRedirect("/")
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return response
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``get_script_prefix()``
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=======================
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.. function:: get_script_prefix()
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Normally, you should always use :func:`~django.urls.reverse` to define URLs
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within your application. However, if your application constructs part of the
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URL hierarchy itself, you may occasionally need to generate URLs. In that
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case, you need to be able to find the base URL of the Django project within
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its web server (normally, :func:`~django.urls.reverse` takes care of this for
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you). In that case, you can call ``get_script_prefix()``, which will return
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the script prefix portion of the URL for your Django project. If your Django
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project is at the root of its web server, this is always ``"/"``.
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.. warning::
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This function **cannot** be used outside of the request-response cycle
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since it relies on values initialized during that cycle.
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