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Refactored URL mapping documentation. 

Reorganized topic document so it introduces concepts form simple to more
complex. Moved reference parts to their own documents.
This commit is contained in:
Ramiro Morales 2012-09-27 19:16:49 -03:00
parent 8a2216648f
commit b6b8a3f66b
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2
docs/ref/index.txt
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@ -22,5 +22,7 @@ API Reference
signals
templates/index
unicode
urlresolvers
urls
utils
validators

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@ -0,0 +1,204 @@
==============================================
``django.core.urlresolvers`` utility functions
==============================================
.. module:: django.core.urlresolvers
reverse()
---------
If you need to use something similar to the :ttag:`url` template tag in
your code, Django provides the following function (in the
:mod:`django.core.urlresolvers` module):
.. function:: reverse(viewname, [urlconf=None, args=None, kwargs=None, current_app=None])
``viewname`` is either the function name (either a function reference, or the
string version of the name, if you used that form in ``urlpatterns``) or the
:ref:`URL pattern name <naming-url-patterns>`. Normally, you won't need to
worry about the ``urlconf`` parameter and will only pass in the positional and
keyword arguments to use in the URL matching. For example::
from django.core.urlresolvers import reverse
def myview(request):
return HttpResponseRedirect(reverse('arch-summary', args=[1945]))
The ``reverse()`` function can reverse a large variety of regular expression
patterns for URLs, but not every possible one. The main restriction at the
moment is that the pattern cannot contain alternative choices using the
vertical bar (``"|"``) character. You can quite happily use such patterns for
matching against incoming URLs and sending them off to views, but you cannot
reverse such patterns.
The ``current_app`` argument allows you to provide a hint to the resolver
indicating the application to which the currently executing view belongs.
This ``current_app`` argument is used as a hint to resolve application
namespaces into URLs on specific application instances, according to the
:ref:`namespaced URL resolution strategy <topics-http-reversing-url-namespaces>`.
You can use ``kwargs`` instead of ``args``. For example::
>>> reverse('admin:app_list', kwargs={'app_label': 'auth'})
'/admin/auth/'
``args`` and ``kwargs`` cannot be passed to ``reverse()`` at the same time.
.. admonition:: Make sure your views are all correct.
As part of working out which URL names map to which patterns, the
``reverse()`` function has to import all of your URLconf files and examine
the name of each view. This involves importing each view function. If
there are *any* errors whilst importing any of your view functions, it
will cause ``reverse()`` to raise an error, even if that view function is
not the one you are trying to reverse.
Make sure that any views you reference in your URLconf files exist and can
be imported correctly. Do not include lines that reference views you
haven't written yet, because those views will not be importable.
.. note::
The string returned by :meth:`~django.core.urlresolvers.reverse` is already
:ref:`urlquoted <uri-and-iri-handling>`. For example::
>>> reverse('cities', args=[u'Orléans'])
'.../Orl%C3%A9ans/'
Applying further encoding (such as :meth:`~django.utils.http.urlquote` or
``urllib.quote``) to the output of :meth:`~django.core.urlresolvers.reverse`
may produce undesirable results.
reverse_lazy()
--------------
.. versionadded:: 1.4
A lazily evaluated version of `reverse()`_.
.. function:: reverse_lazy(viewname, [urlconf=None, args=None, kwargs=None, current_app=None])
It is useful for when you need to use a URL reversal before your project's
URLConf is loaded. Some common cases where this function is necessary are:
* providing a reversed URL as the ``url`` attribute of a generic class-based
view.
* providing a reversed URL to a decorator (such as the ``login_url`` argument
for the :func:`django.contrib.auth.decorators.permission_required`
decorator).
* providing a reversed URL as a default value for a parameter in a function's
signature.
resolve()
---------
The :func:`django.core.urlresolvers.resolve` function can be used for
resolving URL paths to the corresponding view functions. It has the
following signature:
.. function:: resolve(path, urlconf=None)
``path`` is the URL path you want to resolve. As with
:func:`~django.core.urlresolvers.reverse`, you don't need to
worry about the ``urlconf`` parameter. The function returns a
:class:`ResolverMatch` object that allows you
to access various meta-data about the resolved URL.
If the URL does not resolve, the function raises an
:class:`~django.http.Http404` exception.
.. class:: ResolverMatch
.. attribute:: ResolverMatch.func
The view function that would be used to serve the URL
.. attribute:: ResolverMatch.args
The arguments that would be passed to the view function, as
parsed from the URL.
.. attribute:: ResolverMatch.kwargs
The keyword arguments that would be passed to the view
function, as parsed from the URL.
.. attribute:: ResolverMatch.url_name
The name of the URL pattern that matches the URL.
.. attribute:: ResolverMatch.app_name
The application namespace for the URL pattern that matches the
URL.
.. attribute:: ResolverMatch.namespace
The instance namespace for the URL pattern that matches the
URL.
.. attribute:: ResolverMatch.namespaces
The list of individual namespace components in the full
instance namespace for the URL pattern that matches the URL.
i.e., if the namespace is ``foo:bar``, then namespaces will be
``['foo', 'bar']``.
A :class:`ResolverMatch` object can then be interrogated to provide
information about the URL pattern that matches a URL::
# Resolve a URL
match = resolve('/some/path/')
# Print the URL pattern that matches the URL
print(match.url_name)
A :class:`ResolverMatch` object can also be assigned to a triple::
func, args, kwargs = resolve('/some/path/')
One possible use of :func:`~django.core.urlresolvers.resolve` would be to test
whether a view would raise a ``Http404`` error before redirecting to it::
from urlparse import urlparse
from django.core.urlresolvers import resolve
from django.http import HttpResponseRedirect, Http404
def myview(request):
next = request.META.get('HTTP_REFERER', None) or '/'
response = HttpResponseRedirect(next)
# modify the request and response as required, e.g. change locale
# and set corresponding locale cookie
view, args, kwargs = resolve(urlparse(next)[2])
kwargs['request'] = request
try:
view(*args, **kwargs)
except Http404:
return HttpResponseRedirect('/')
return response
permalink()
-----------
The :func:`django.db.models.permalink` decorator is useful for writing short
methods that return a full URL path. For example, a model's
``get_absolute_url()`` method. See :func:`django.db.models.permalink` for more.
get_script_prefix()
-------------------
.. function:: get_script_prefix()
Normally, you should always use :func:`~django.core.urlresolvers.reverse` or
:func:`~django.db.models.permalink` to define URLs within your application.
However, if your application constructs part of the URL hierarchy itself, you
may occasionally need to generate URLs. In that case, you need to be able to
find the base URL of the Django project within its Web server
(normally, :func:`~django.core.urlresolvers.reverse` takes care of this for
you). In that case, you can call ``get_script_prefix()``, which will return the
script prefix portion of the URL for your Django project. If your Django
project is at the root of its Web server, this is always ``"/"``.

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@ -0,0 +1,139 @@
======================================
``django.conf.urls`` utility functions
======================================
.. module:: django.conf.urls
.. versionchanged:: 1.4
Starting with Django 1.4 functions ``patterns``, ``url``, ``include`` plus
the ``handler*`` symbols described below live in the ``django.conf.urls``
module.
Until Django 1.3 they were located in ``django.conf.urls.defaults``. You
still can import them from there but it will be removed in Django 1.6.
patterns()
----------
.. function:: patterns(prefix, pattern_description, ...)
A function that takes a prefix, and an arbitrary number of URL patterns, and
returns a list of URL patterns in the format Django needs.
The first argument to ``patterns()`` is a string ``prefix``. See
:ref:`The view prefix <urlpatterns-view-prefix>`.
The remaining arguments should be tuples in this format::
(regular expression, Python callback function [, optional_dictionary [, optional_name]])
The ``optional_dictionary`` and ``optional_name`` parameters are described in
:ref:`Passing extra options to view functions <views-extra-options>`.
.. note::
Because `patterns()` is a function call, it accepts a maximum of 255
arguments (URL patterns, in this case). This is a limit for all Python
function calls. This is rarely a problem in practice, because you'll
typically structure your URL patterns modularly by using `include()`
sections. However, on the off-chance you do hit the 255-argument limit,
realize that `patterns()` returns a Python list, so you can split up the
construction of the list.
::
urlpatterns = patterns('',
...
)
urlpatterns += patterns('',
...
)
Python lists have unlimited size, so there's no limit to how many URL
patterns you can construct. The only limit is that you can only create 254
at a time (the 255th argument is the initial prefix argument).
url()
-----
.. function:: url(regex, view, kwargs=None, name=None, prefix='')
You can use the ``url()`` function, instead of a tuple, as an argument to
``patterns()``. This is convenient if you want to specify a name without the
optional extra arguments dictionary. For example::
urlpatterns = patterns('',
url(r'^index/$', index_view, name="main-view"),
...
)
This function takes five arguments, most of which are optional::
url(regex, view, kwargs=None, name=None, prefix='')
See :ref:`Naming URL patterns <naming-url-patterns>` for why the ``name``
parameter is useful.
The ``prefix`` parameter has the same meaning as the first argument to
``patterns()`` and is only relevant when you're passing a string as the
``view`` parameter.
include()
---------
.. function:: include(<module or pattern_list>)
A function that takes a full Python import path to another URLconf module that
should be "included" in this place.
:func:`include` also accepts as an argument an iterable that returns URL
patterns.
See :ref:`Including other URLconfs <including-other-urlconfs>`.
handler403
----------
.. data:: handler403
A callable, or a string representing the full Python import path to the view
that should be called if the user doesn't have the permissions required to
access a resource.
By default, this is ``'django.views.defaults.permission_denied'``. That default
value should suffice.
See the documentation about :ref:`the 403 (HTTP Forbidden) view
<http_forbidden_view>` for more information.
.. versionadded:: 1.4
``handler403`` is new in Django 1.4.
handler404
----------
.. data:: handler404
A callable, or a string representing the full Python import path to the view
that should be called if none of the URL patterns match.
By default, this is ``'django.views.defaults.page_not_found'``. That default
value should suffice.
See the documentation about :ref:`the 404 (HTTP Not Found) view
<http_not_found_view>` for more information.
handler500
----------
.. data:: handler500
A callable, or a string representing the full Python import path to the view
that should be called in case of server errors. Server errors happen when you
have runtime errors in view code.
By default, this is ``'django.views.defaults.server_error'``. That default
value should suffice.
See the documentation about :ref:`the 500 (HTTP Internal Server Error) view
<http_internal_server_error_view>` for more information.

483
docs/topics/http/urls.txt
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@ -2,8 +2,6 @@
URL dispatcher
==============
.. module:: django.core.urlresolvers
A clean, elegant URL scheme is an important detail in a high-quality Web
application. Django lets you design URLs however you want, with no framework
limitations.
@ -160,7 +158,8 @@ vs. non-named groups in a regular expression:
2. Otherwise, it will pass all non-named arguments as positional arguments.
In both cases, any extra keyword arguments that have been given as per `Passing extra options to view functions`_ (below) will also be passed to the view.
In both cases, any extra keyword arguments that have been given as per `Passing
extra options to view functions`_ (below) will also be passed to the view.
What the URLconf searches against
=================================
@ -215,7 +214,6 @@ Performance
Each regular expression in a ``urlpatterns`` is compiled the first time it's
accessed. This makes the system blazingly fast.
Syntax of the urlpatterns variable
==================================
@ -223,154 +221,35 @@ Syntax of the urlpatterns variable
:func:`django.conf.urls.patterns`. Always use ``patterns()`` to create
the ``urlpatterns`` variable.
``django.conf.urls`` utility functions
======================================
.. module:: django.conf.urls
.. deprecated:: 1.4
Starting with Django 1.4 functions ``patterns``, ``url``, ``include`` plus
the ``handler*`` symbols described below live in the ``django.conf.urls``
module.
Until Django 1.3 they were located in ``django.conf.urls.defaults``. You
still can import them from there but it will be removed in Django 1.6.
patterns
--------
.. function:: patterns(prefix, pattern_description, ...)
A function that takes a prefix, and an arbitrary number of URL patterns, and
returns a list of URL patterns in the format Django needs.
The first argument to ``patterns()`` is a string ``prefix``. See
`The view prefix`_ below.
The remaining arguments should be tuples in this format::
(regular expression, Python callback function [, optional_dictionary [, optional_name]])
The ``optional_dictionary`` and ``optional_name`` parameters are described in
`Passing extra options to view functions`_ below.
.. note::
Because `patterns()` is a function call, it accepts a maximum of 255
arguments (URL patterns, in this case). This is a limit for all Python
function calls. This is rarely a problem in practice, because you'll
typically structure your URL patterns modularly by using `include()`
sections. However, on the off-chance you do hit the 255-argument limit,
realize that `patterns()` returns a Python list, so you can split up the
construction of the list.
::
urlpatterns = patterns('',
...
)
urlpatterns += patterns('',
...
)
Python lists have unlimited size, so there's no limit to how many URL
patterns you can construct. The only limit is that you can only create 254
at a time (the 255th argument is the initial prefix argument).
url
---
.. function:: url(regex, view, kwargs=None, name=None, prefix='')
You can use the ``url()`` function, instead of a tuple, as an argument to
``patterns()``. This is convenient if you want to specify a name without the
optional extra arguments dictionary. For example::
urlpatterns = patterns('',
url(r'^index/$', index_view, name="main-view"),
...
)
This function takes five arguments, most of which are optional::
url(regex, view, kwargs=None, name=None, prefix='')
See `Naming URL patterns`_ for why the ``name`` parameter is useful.
The ``prefix`` parameter has the same meaning as the first argument to
``patterns()`` and is only relevant when you're passing a string as the
``view`` parameter.
include
-------
.. function:: include(<module or pattern_list>)
A function that takes a full Python import path to another URLconf module that
should be "included" in this place.
:func:`include` also accepts as an argument an iterable that returns URL
patterns.
See `Including other URLconfs`_ below.
Error handling
==============
When Django can't find a regex matching the requested URL, or when an
exception is raised, Django will invoke an error-handling view. The
views to use for these cases are specified by three variables which can
be set in your root URLconf. Setting these variables in any other
URLconf will have no effect.
exception is raised, Django will invoke an error-handling view.
The views to use for these cases are specified by three variables. Their
default values should suffice for most projects, but further customization is
possible by assigning values to them.
See the documentation on :ref:`customizing error views
<customizing-error-views>` for more details.
<customizing-error-views>` for the full details.
handler403
----------
Such values can be set in your root URLconf. Setting these variables in any
other URLconf will have no effect.
.. data:: handler403
Values must be callables, or strings representing the full Python import path
to the view that should be called to handle the error condition at hand.
A callable, or a string representing the full Python import path to the view
that should be called if the user doesn't have the permissions required to
access a resource.
The variables are:
By default, this is ``'django.views.defaults.permission_denied'``. That default
value should suffice.
See the documentation about :ref:`the 403 (HTTP Forbidden) view
<http_forbidden_view>` for more information.
* ``handler404`` -- See :data:`django.conf.urls.handler404`.
* ``handler500`` -- See :data:`django.conf.urls.handler500`.
* ``handler403`` -- See :data:`django.conf.urls.handler403`.
.. versionadded:: 1.4
``handler403`` is new in Django 1.4.
handler404
----------
.. data:: handler404
A callable, or a string representing the full Python import path to the view
that should be called if none of the URL patterns match.
By default, this is ``'django.views.defaults.page_not_found'``. That default
value should suffice.
See the documentation about :ref:`the 404 (HTTP Not Found) view
<http_not_found_view>` for more information.
handler500
----------
.. data:: handler500
A callable, or a string representing the full Python import path to the view
that should be called in case of server errors. Server errors happen when you
have runtime errors in view code.
By default, this is ``'django.views.defaults.server_error'``. That default
value should suffice.
See the documentation about :ref:`the 500 (HTTP Internal Server Error) view
<http_internal_server_error_view>` for more information.
.. _urlpatterns-view-prefix:
The view prefix
===============
@ -437,6 +316,8 @@ New::
(r'^tag/(?P<tag>\w+)/$', 'tag'),
)
.. _including-other-urlconfs:
Including other URLconfs
========================
@ -459,13 +340,14 @@ itself. It includes a number of other URLconfs::
Note that the regular expressions in this example don't have a ``$``
(end-of-string match character) but do include a trailing slash. Whenever
Django encounters ``include()``, it chops off whatever part of the URL matched
up to that point and sends the remaining string to the included URLconf for
further processing.
Django encounters ``include()`` (:func:`django.conf.urls.include()`), it chops
off whatever part of the URL matched up to that point and sends the remaining
string to the included URLconf for further processing.
Another possibility is to include additional URL patterns not by specifying the
URLconf Python module defining them as the `include`_ argument but by using
directly the pattern list as returned by `patterns`_ instead. For example::
URLconf Python module defining them as the ``include()`` argument but by using
directly the pattern list as returned by :func:`~django.conf.urls.patterns`
instead. For example::
from django.conf.urls import patterns, url, include
@ -510,57 +392,7 @@ the following example is valid::
In the above example, the captured ``"username"`` variable is passed to the
included URLconf, as expected.
.. _topics-http-defining-url-namespaces:
Defining URL namespaces
-----------------------
When you need to deploy multiple instances of a single application, it can be
helpful to be able to differentiate between instances. This is especially
important when using :ref:`named URL patterns <naming-url-patterns>`, since
multiple instances of a single application will share named URLs. Namespaces
provide a way to tell these named URLs apart.
A URL namespace comes in two parts, both of which are strings:
* An **application namespace**. This describes the name of the application
that is being deployed. Every instance of a single application will have
the same application namespace. For example, Django's admin application
has the somewhat predictable application namespace of ``admin``.
* An **instance namespace**. This identifies a specific instance of an
application. Instance namespaces should be unique across your entire
project. However, an instance namespace can be the same as the
application namespace. This is used to specify a default instance of an
application. For example, the default Django Admin instance has an
instance namespace of ``admin``.
URL Namespaces can be specified in two ways.
Firstly, you can provide the application and instance namespace as arguments
to ``include()`` when you construct your URL patterns. For example,::
(r'^help/', include('apps.help.urls', namespace='foo', app_name='bar')),
This will include the URLs defined in ``apps.help.urls`` into the application
namespace ``bar``, with the instance namespace ``foo``.
Secondly, you can include an object that contains embedded namespace data. If
you ``include()`` a ``patterns`` object, that object will be added to the
global namespace. However, you can also ``include()`` an object that contains
a 3-tuple containing::
(<patterns object>, <application namespace>, <instance namespace>)
This will include the nominated URL patterns into the given application and
instance namespace. For example, the ``urls`` attribute of Django's
:class:`~django.contrib.admin.AdminSite` object returns a 3-tuple that contains
all the patterns in an admin site, plus the name of the admin instance, and the
application namespace ``admin``.
Once you have defined namespaced URLs, you can reverse them. For details on
reversing namespaced urls, see the documentation on :ref:`reversing namespaced
URLs <topics-http-reversing-url-namespaces>`.
.. _views-extra-options:
Passing extra options to view functions
=======================================
@ -698,10 +530,10 @@ view::
)
This is completely valid, but it leads to problems when you try to do reverse
URL matching (through the ``permalink()`` decorator or the :ttag:`url` template
tag). Continuing this example, if you wanted to retrieve the URL for the
``archive`` view, Django's reverse URL matcher would get confused, because *two*
URL patterns point at that view.
URL matching (through the :func:`~django.db.models.permalink` decorator or the
:ttag:`url` template tag). Continuing this example, if you wanted to retrieve
the URL for the ``archive`` view, Django's reverse URL matcher would get
confused, because *two* URL patterns point at that view.
To solve this problem, Django supports **named URL patterns**. That is, you can
give a name to a URL pattern in order to distinguish it from other patterns
@ -741,10 +573,36 @@ not restricted to valid Python names.
name, will decrease the chances of collision. We recommend something like
``myapp-comment`` instead of ``comment``.
.. _topics-http-reversing-url-namespaces:
.. _topics-http-defining-url-namespaces:
URL namespaces
--------------
==============
Introduction
------------
When you need to deploy multiple instances of a single application, it can be
helpful to be able to differentiate between instances. This is especially
important when using :ref:`named URL patterns <naming-url-patterns>`, since
multiple instances of a single application will share named URLs. Namespaces
provide a way to tell these named URLs apart.
A URL namespace comes in two parts, both of which are strings:
.. glossary::
application namespace
This describes the name of the application that is being deployed. Every
instance of a single application will have the same application namespace.
For example, Django's admin application has the somewhat predictable
application namespace of ``admin``.
instance namespace
This identifies a specific instance of an application. Instance namespaces
should be unique across your entire project. However, an instance namespace
can be the same as the application namespace. This is used to specify a
default instance of an application. For example, the default Django Admin
instance has an instance namespace of ``admin``.
Namespaced URLs are specified using the ``:`` operator. For example, the main
index page of the admin application is referenced using ``admin:index``. This
@ -754,6 +612,11 @@ Namespaces can also be nested. The named URL ``foo:bar:whiz`` would look for
a pattern named ``whiz`` in the namespace ``bar`` that is itself defined within
the top-level namespace ``foo``.
.. _topics-http-reversing-url-namespaces:
Reversing namespaced URLs
-------------------------
When given a namespaced URL (e.g. ``myapp:index``) to resolve, Django splits
the fully qualified name into parts, and then tries the following lookup:
@ -787,6 +650,9 @@ If there are nested namespaces, these steps are repeated for each part of the
namespace until only the view name is unresolved. The view name will then be
resolved into a URL in the namespace that has been found.
Example
~~~~~~~
To show this resolution strategy in action, consider an example of two instances
of ``myapp``: one called ``foo``, and one called ``bar``. ``myapp`` has a main
index page with a URL named `index`. Using this setup, the following lookups are
@ -818,209 +684,28 @@ following would happen:
* ``foo:index`` will again resolve to the index page of the instance ``foo``.
URL namespaces and included URLconfs
------------------------------------
``django.core.urlresolvers`` utility functions
==============================================
URL namespaces of included URLconfs can be specified in two ways.
.. currentmodule:: django.core.urlresolvers
Firstly, you can provide the application and instance namespace as arguments
to ``include()`` when you construct your URL patterns. For example,::
reverse()
---------
(r'^help/', include('apps.help.urls', namespace='foo', app_name='bar')),
If you need to use something similar to the :ttag:`url` template tag in
your code, Django provides the following function (in the
:mod:`django.core.urlresolvers` module):
This will include the URLs defined in ``apps.help.urls`` into the application
namespace ``bar``, with the instance namespace ``foo``.
.. function:: reverse(viewname, [urlconf=None, args=None, kwargs=None, current_app=None])
Secondly, you can include an object that contains embedded namespace data. If
you ``include()`` a ``patterns`` object, that object will be added to the
global namespace. However, you can also ``include()`` an object that contains
a 3-tuple containing::
``viewname`` is either the function name (either a function reference, or the
string version of the name, if you used that form in ``urlpatterns``) or the
`URL pattern name`_. Normally, you won't need to worry about the
``urlconf`` parameter and will only pass in the positional and keyword
arguments to use in the URL matching. For example::
(<patterns object>, <application namespace>, <instance namespace>)
from django.core.urlresolvers import reverse
def myview(request):
return HttpResponseRedirect(reverse('arch-summary', args=[1945]))
.. _URL pattern name: `Naming URL patterns`_
The ``reverse()`` function can reverse a large variety of regular expression
patterns for URLs, but not every possible one. The main restriction at the
moment is that the pattern cannot contain alternative choices using the
vertical bar (``"|"``) character. You can quite happily use such patterns for
matching against incoming URLs and sending them off to views, but you cannot
reverse such patterns.
The ``current_app`` argument allows you to provide a hint to the resolver
indicating the application to which the currently executing view belongs.
This ``current_app`` argument is used as a hint to resolve application
namespaces into URLs on specific application instances, according to the
:ref:`namespaced URL resolution strategy <topics-http-reversing-url-namespaces>`.
You can use ``kwargs`` instead of ``args``. For example::
>>> reverse('admin:app_list', kwargs={'app_label': 'auth'})
'/admin/auth/'
``args`` and ``kwargs`` cannot be passed to ``reverse()`` at the same time.
.. admonition:: Make sure your views are all correct.
As part of working out which URL names map to which patterns, the
``reverse()`` function has to import all of your URLconf files and examine
the name of each view. This involves importing each view function. If
there are *any* errors whilst importing any of your view functions, it
will cause ``reverse()`` to raise an error, even if that view function is
not the one you are trying to reverse.
Make sure that any views you reference in your URLconf files exist and can
be imported correctly. Do not include lines that reference views you
haven't written yet, because those views will not be importable.
.. note::
The string returned by :meth:`~django.core.urlresolvers.reverse` is already
:ref:`urlquoted <uri-and-iri-handling>`. For example::
>>> reverse('cities', args=[u'Orléans'])
'.../Orl%C3%A9ans/'
Applying further encoding (such as :meth:`~django.utils.http.urlquote` or
``urllib.quote``) to the output of :meth:`~django.core.urlresolvers.reverse`
may produce undesirable results.
reverse_lazy()
--------------
.. versionadded:: 1.4
A lazily evaluated version of `reverse()`_.
.. function:: reverse_lazy(viewname, [urlconf=None, args=None, kwargs=None, current_app=None])
It is useful for when you need to use a URL reversal before your project's
URLConf is loaded. Some common cases where this function is necessary are:
* providing a reversed URL as the ``url`` attribute of a generic class-based
view.
* providing a reversed URL to a decorator (such as the ``login_url`` argument
for the :func:`django.contrib.auth.decorators.permission_required`
decorator).
* providing a reversed URL as a default value for a parameter in a function's
signature.
resolve()
---------
The :func:`django.core.urlresolvers.resolve` function can be used for
resolving URL paths to the corresponding view functions. It has the
following signature:
.. function:: resolve(path, urlconf=None)
``path`` is the URL path you want to resolve. As with
:func:`~django.core.urlresolvers.reverse`, you don't need to
worry about the ``urlconf`` parameter. The function returns a
:class:`ResolverMatch` object that allows you
to access various meta-data about the resolved URL.
If the URL does not resolve, the function raises an
:class:`~django.http.Http404` exception.
.. class:: ResolverMatch
.. attribute:: ResolverMatch.func
The view function that would be used to serve the URL
.. attribute:: ResolverMatch.args
The arguments that would be passed to the view function, as
parsed from the URL.
.. attribute:: ResolverMatch.kwargs
The keyword arguments that would be passed to the view
function, as parsed from the URL.
.. attribute:: ResolverMatch.url_name
The name of the URL pattern that matches the URL.
.. attribute:: ResolverMatch.app_name
The application namespace for the URL pattern that matches the
URL.
.. attribute:: ResolverMatch.namespace
The instance namespace for the URL pattern that matches the
URL.
.. attribute:: ResolverMatch.namespaces
The list of individual namespace components in the full
instance namespace for the URL pattern that matches the URL.
i.e., if the namespace is ``foo:bar``, then namespaces will be
``['foo', 'bar']``.
A :class:`ResolverMatch` object can then be interrogated to provide
information about the URL pattern that matches a URL::
# Resolve a URL
match = resolve('/some/path/')
# Print the URL pattern that matches the URL
print(match.url_name)
A :class:`ResolverMatch` object can also be assigned to a triple::
func, args, kwargs = resolve('/some/path/')
One possible use of :func:`~django.core.urlresolvers.resolve` would be to test
whether a view would raise a ``Http404`` error before redirecting to it::
from urlparse import urlparse
from django.core.urlresolvers import resolve
from django.http import HttpResponseRedirect, Http404
def myview(request):
next = request.META.get('HTTP_REFERER', None) or '/'
response = HttpResponseRedirect(next)
# modify the request and response as required, e.g. change locale
# and set corresponding locale cookie
view, args, kwargs = resolve(urlparse(next)[2])
kwargs['request'] = request
try:
view(*args, **kwargs)
except Http404:
return HttpResponseRedirect('/')
return response
permalink()
-----------
The :func:`django.db.models.permalink` decorator is useful for writing short
methods that return a full URL path. For example, a model's
``get_absolute_url()`` method. See :func:`django.db.models.permalink` for more.
get_script_prefix()
-------------------
.. function:: get_script_prefix()
Normally, you should always use :func:`~django.core.urlresolvers.reverse` or
:func:`~django.db.models.permalink` to define URLs within your application.
However, if your application constructs part of the URL hierarchy itself, you
may occasionally need to generate URLs. In that case, you need to be able to
find the base URL of the Django project within its Web server
(normally, :func:`~django.core.urlresolvers.reverse` takes care of this for
you). In that case, you can call ``get_script_prefix()``, which will return the
script prefix portion of the URL for your Django project. If your Django
project is at the root of its Web server, this is always ``"/"``.
This will include the nominated URL patterns into the given application and
instance namespace. For example, the ``urls`` attribute of Django's
:class:`~django.contrib.admin.AdminSite` object returns a 3-tuple that contains
all the patterns in an admin site, plus the name of the admin instance, and the
application namespace ``admin``.