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194 lines
7.0 KiB
Plaintext
194 lines
7.0 KiB
Plaintext
==============================================
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``django.core.urlresolvers`` utility functions
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==============================================
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.. module:: django.core.urlresolvers
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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`` is either the function name (either a function reference, or the
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string version of the name, if you used that form in ``urlpatterns``) or the
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:ref:`URL pattern name <naming-url-patterns>`. Normally, you won't need to
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worry about the ``urlconf`` parameter and will only pass in the positional and
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keyword arguments to use in the URL matching. For example::
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from django.core.urlresolvers import reverse
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def myview(request):
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return HttpResponseRedirect(reverse('arch-summary', args=[1945]))
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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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You can use ``kwargs`` instead of ``args``. For example::
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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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.. admonition:: Make sure your views are all correct.
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As part of working out which URL names map to which patterns, the
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``reverse()`` function has to import all of your URLconf files and examine
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the name of each view. This involves importing each view function. If
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there are *any* errors whilst importing any of your view functions, it
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will cause ``reverse()`` to raise an error, even if that view function is
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not the one you are trying to reverse.
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Make sure that any views you reference in your URLconf files exist and can
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be imported correctly. Do not include lines that reference views you
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haven't written yet, because those views will not be importable.
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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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>>> reverse('cities', args=[u'Orléans'])
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'.../Orl%C3%A9ans/'
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Applying further encoding (such as :meth:`~django.utils.http.urlquote` or
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``urllib.quote``) to the output of ``reverse()`` may produce undesirable
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results.
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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.core.urlresolvers.reverse`, you don't need to
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worry about the ``urlconf`` parameter. The function returns a
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:class:`ResolverMatch` object that allows you
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to access various meta-data about the resolved URL.
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If the URL does not resolve, the function raises a
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:exc:`~django.core.urlresolvers.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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The 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.url_name
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The name of the URL pattern that matches the URL.
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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.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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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.core.urlresolvers.resolve` would be to test
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whether a view would raise a ``Http404`` error before redirecting to it::
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from urlparse import urlparse
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from django.core.urlresolvers import resolve
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from django.http import HttpResponseRedirect, Http404
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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(urlparse(next)[2])
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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.core.urlresolvers.reverse` to
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define URLs within your application. However, if your application constructs
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part of the URL hierarchy itself, you may occasionally need to generate URLs.
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In that case, you need to be able to find the base URL of the Django project
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within its Web server (normally, :func:`~django.core.urlresolvers.reverse`
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takes care of this for you). In that case, you can call
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``get_script_prefix()``, which will return the script prefix portion of the URL
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for your Django project. If your Django project is at the root of its web
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server, this is always ``"/"``.
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