django-url-tools 0.0.3

================
Django URL tools
================

------------------------------------------------------
Django helper tools for dealing with URLs in templates
------------------------------------------------------

.. contents::

Overview
========

Django URL tools are context processors, and template tags that help you deal
with URL manipulations in templates. The heavy lifting is done by the
``url_tools.helper.UrlHelper`` class which wraps around ``urllib``,
``urlparse``, and Django's ``QueryDict`` to provide facilities for parsing and
manipulating URLs.

Installation
============

Simply install the ``django-url-tools`` package using ``easy_install`` or
``pip``::

pip install django-url-tools

Configuring your Django project
===============================

To use the context processor, add the following to the middlewares stack::

TEMPLATE_CONTEXT_PROCESSORS = (
...
'url_tools.context_processors.current_url',
)

If you want to use the template tags, add ``url_tools`` to installed apps::

INSTALLED_APPS = (
...
'url_tools',
)

UrlHelper class
===============

``UrlHelper`` class implements all methods for manipulating URLs that are used
in other parts of this app. You can also use this class directly by importing
it from the ``helper`` module::

from url_tools.helper import UrlHelper

``UrlHelper`` constructor accepts only one argument, which is the full path of
the URL you want to manipulate. Although we can technically make ``UrlHelper``
deal with full absolute URLs, we have opted to implement only methods for
dealing with paths instead. Therefore, if you pass UrlHelper an full URL with
scheme, host, port, and user credentials, it would still only use the path,
query parameters, and the fragment identifiers.

The class has following properties:

+ ``path``: URL's path without query string and fragment identifier
+ ``fragment``: URL's fragment identifier (without the pound character ``#``)
+ ``query_dict``: ``QueryDict`` instance containing the URL's query parameters
+ ``query``: similar to ``query_dict`` but also does more when assigning
+ ``query_string``: URL's query string
+ ``hash``: MD5 hexdigest of the full path including query parameters

UrlHelper.path
--------------

This is a simple string property containing the URl's path. For example, in an
URL ``'/foo/bar?baz=1#boo'``, the property contains ``'/foo/bar'``.

UrlHelper.fragment
------------------

Contains the fragment identifier. In the URL ``'/foo/bar?baz=1#boo'``, this
property contains ``'foo'``.

UrlHelper.query_dict
--------------------

Contains the query parameters parsed from the URL in form of
``django.http.request.QueryDict`` instance. You can read more about the
``QueryDict`` API in `Django documentation on QueryDict`_.

UrlHelper.query
---------------

This is a property returns the ``UrlHelper.query_dict`` when read, but
overrides it when assigend a normal dictionary or a string. For example::

u = UrlHelper('/foo/bar')
u.query = 'foo=1&bar=2'
# or
u.query = dict(foo=1, bar=2)

Both above assignment work.

UrlHelper.query_string
----------------------

This property returns a query string when read, and behaves the same way as the
query property when assigning a string. However, you cannot assign dictionaries
to this property. ::

u = UrlHelper('/foo/bar')
u.query_string = 'foo=1&bar=2' # this works
u.query_string = dict(foo=1, bar=2) # but this doesn't

UrlHelper.hash
--------------

Returns the MD5 hexdigest of the full path including query parameters. This can
be useful for use with caching and other situations where we need to
differentiate same paths with different query parameters. ::

u = UrlHelper('/foo/bar')
u.query = dict(foo=1) # URL is now '/foo/bar?foo=1'
u.hash # returns '06f0a42bdd474f053fb1343165a31d42'

UrlHelper.get_query_string(**kwargs)
------------------------------------

This method returns the query string using ``QueryDict``'s ``urlencode()``
method. Any keyword parameters you pass to this method are forwarded to the
``urlencode()`` method. Currently, the only keyword argument is ``safe`` which
instructs the method to not escape specified characters.

UrlHelper.get_query_data()
--------------------------

Returns the ``UrlHelper.query_dict`` property. This methods exist mostly to
help customize the behavior of ``UrlHelper.query`` in subclasses, since the
getter calls this method instead of returning the ``query_dict`` property
directly.

UrlHelper.update_query_data(**kwargs)
-------------------------------------

This method takes any number of keyword arguments and updates the
``UrlHelper.query_dict`` instance. Since, unlike Python dictionary, each
``QueryDict`` key can have multple values, you can pass multiple values as
Python iterables such as lists or tuples. For example::

u = UrlHelper('/foo')
u.update_query_data(bar=[1, 2, 3])
u.query_string # returns '/foo?bar=1&bar=2&bar=3'

UrlHelper.get_path()
--------------------

Returns the ``UrlHelper.path`` property. This method exist to help
customization of ``UrlHelper.get_full_path()`` method in subclasses. Other than
that, it's the same as using the ``path`` property.

UrlHelper.get_full_path(**kwargs)
---------------------------------

Returns the full path with query string and fragment identifier (if any). The
keyword arguments passed to this function are passed onto
``UrlHelper.get_query_string()`` method, and therefore to
``QueryDict.urlencode()`` method.

UrlHelper.get_full_quoted_path(**kwargs)
----------------------------------------

Same as ``UrlHelper.get_full_path()`` method, but returns the full path quoted
so that it can be used as an URL parameter value.

ContextProcessors
=================

current_url
-----------

The ``current_url`` context processor will add a new variable to the template's
context. This variable is called ``current_url``, and it's an ``UrlHelper``
instance. Therefore, this variable has all the properties and methods of the
``UrlHelper`` class. For instance, if we are currently on ``/foo/bar?baz=1``
path, you can do the following in a template::

{{ current_url.query_string }} {# renders `baz=1` #}
{{ current_url.get_path }} {# renders `/foo/bar` #}

and so on. The variable itself renders as full relative path with query string
and fragment identifier (identical to output of ``UrlHelper.get_full_path()``
method).

Template tags
=============

To use the template tags, first load the ``urls`` library::

{% load urls %}

URL tools currently has only one template tag, which is an assignment tag.

{% add_params %}
----------------

This template tag outputs a path with query string parameters given as keyword
arguments. For instance, if we are on a page at ``/foo``, we can use this tag::

{% add_params request.get_full_path foo='bar' %}

and the output would be::

``/foo?foo=bar``

Existing URL parameters are overridden by the ones specified as keyword
arguments.

{% url_params %}
----------------

This tag is used as an assignment tag. Its first argument is an URL, followed
by any number of keyword arguments that represent the URL parameters. For
example, if we are requesting a page on ``'/foo'`` path, and do this::

{% url_params request.get_full_path foo='bar' as new_url %}

We can use the ``new_url`` variable from that point on, that represents the
``/foo?foo=bar`` URL. To use this with your configured URLs, you can use the
built-in ``url`` tag::

{% url 'foo' as foo_url %}
{% url_arams foo_url foo='bar' as foo_url %}

If the reverse match for ``'foo'`` is, say, ``'/foo'``, then the ``foo_url``
variable will, predictably, contain ``'/foo?foo=bar'``.

This tag will override existing parameters rather than adding new values for
existing keywords. Therefore, you can safely use it to set URL parameters
whether they exist or not. This is typically useful when you are building URLs
for controls like pagers. Regardless of whether there is a ``page`` parameter
or not, setting it with ``url_params`` tag will correctly set the parameter to
desired value::

{% url_params current_url page=2 %}
{# this works for both ``/foo?page=1`` and just ``/foo`` #}

Reporting bugs
==============

Please report any bugs to our BitBucket `issue tracker`_.

.. _Django documentation on QueryDict: https://docs.djangoproject.com/en/dev/ref/request-response/?from=olddocs#querydict-objects
.. _issue tracker: https://bitbucket.org/monwara/django-url-tools/issues