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django/docs/newforms.txt
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====================
The newforms library
====================
``django.newforms`` is a new replacement for ``django.forms``, the old Django
form/manipulator/validation framework. This document explains how to use this
new form library.
Migration plan
==============
``django.newforms`` currently is only available in the Django development version
-- i.e., it's not available in the Django 0.95 release. For the next Django
release, our plan is to do the following:
* Move the current ``django.forms`` to ``django.oldforms``. This will allow
for an eased migration of form code. You'll just have to change your
import statements::
from django import forms # old
from django import oldforms as forms # new
* Move the current ``django.newforms`` to ``django.forms``.
* We will remove ``django.oldforms`` in the release *after* the next Django
release -- the release that comes after the release in which we're
creating ``django.oldforms``.
With this in mind, we recommend you use the following import statement when
using ``django.newforms``::
from django import newforms as forms
This way, your code can refer to the ``forms`` module, and when
``django.newforms`` is renamed to ``django.forms``, you'll only have to change
your ``import`` statements.
If you prefer "``import *``" syntax, you can do the following::
from django.newforms import *
This will import all fields, widgets, form classes and other various utilities
into your local namespace. Some people find this convenient; others find it
too messy. The choice is yours.
Overview
========
As the ``django.forms`` ("manipulators") system before it, ``django.newforms``
is intended to handle HTML form display, validation and redisplay. It's what
you use if you want to perform server-side validation for an HTML form.
For example, if your Web site has a contact form that visitors can use to
send you e-mail, you'd use this library to implement the display of the HTML
form fields, along with the form validation. Any time you need to use an HTML
``<form>``, you can use this library.
The library deals with these concepts:
* **Widget** -- A class that corresponds to an HTML form widget, e.g.
``<input type="text">`` or ``<textarea>``. This handles rendering of the
widget as HTML.
* **Field** -- A class that is responsible for doing validation, e.g.
an ``EmailField`` that makes sure its data is a valid e-mail address.
* **Form** -- A collection of fields that knows how to validate itself and
display itself as HTML.
Form objects
============
The primary way of using the ``newforms`` library is to create a form object.
Do this by subclassing ``django.newforms.Form`` and specifying the form's
fields, in a declarative style that you'll be familiar with if you've used
Django database models. In this section, we'll iteratively develop a form
object that you might to implement "contact me" functionality on your personal
Web site.
Start with this basic ``Form`` subclass, which we'll call ``ContactForm``::
from django import newforms as forms
class ContactForm(forms.Form):
subject = forms.CharField(max_length=100)
message = forms.CharField()
sender = forms.EmailField()
cc_myself = forms.BooleanField()
A form is composed of ``Field`` objects. In this case, our form has four
fields: ``subject``, ``message``, ``sender`` and ``cc_myself``. We'll explain
the different types of fields -- e.g., ``CharField`` and ``EmailField`` --
shortly.
Outputting forms as HTML
------------------------
The first thing we can do with this is output it as HTML. To do so, instantiate
it and ``print`` it::
>>> f = ContactForm()
>>> print f
<tr><td><label for="id_subject">Subject:</label></td><td><input id="id_subject" type="text" name="subject" maxlength="100" /></td></tr>
<tr><td><label for="id_message">Message:</label></td><td><input type="text" name="message" id="id_message" /></td></tr>
<tr><td><label for="id_sender">Sender:</label></td><td><input type="text" name="sender" id="id_sender" /></td></tr>
<tr><td><label for="id_cc_myself">Cc myself:</label></td><td><input type="checkbox" name="cc_myself" id="id_cc_myself" /></td></tr>
This default output is a two-column HTML table, with a ``<tr>`` for each field.
Notice the following:
* For flexibility, the output does *not* include the ``<table>`` and
``</table>`` tags, nor does it include the ``<form>`` and ``</form>``
tags or an ``<input type="submit">`` tag. It's your job to do that.
* Each field type has a default HTML representation. ``CharField`` and
``EmailField`` are represented by an ``<input type="text">``.
``BooleanField`` is represented by an ``<input type="checkbox">``. Note
these are merely sensible defaults; you can specify which HTML to use for
a given field by using ``widgets``, which we'll explain shortly.
* The HTML ``name`` for each tag is taken directly from its attribute name
in the ``ContactForm`` class.
* The text label for each field -- e.g. ``'Subject:'``, ``'Message:'`` and
``'CC myself:'`` is generated from the field name by converting all
underscores to spaces and upper-casing the first letter. Again, note
these are merely sensible defaults; you can also specify labels manually.
* Each text label is surrounded in an HTML ``<label>`` tag, which points
to the appropriate form field via its ``id``. Its ``id``, in turn, is
generated by prepending ``'id_'`` to the field name. The ``id``
attributes and ``<label>`` tags are included in the output by default, to
follow best practices, but you can change that behavior.
Although ``<table>`` output is the default output style when you ``print`` a
form, other output styles are available. Each style is available as a method on
a form object, and each rendering method returns a Unicode object.
``as_p()``
~~~~~~~~~~
``Form.as_p()`` renders the form as a series of ``<p>`` tags, with each ``<p>``
containing one field::
>>> f = ContactForm()
>>> f.as_p()
u'<p><label for="id_subject">Subject:</label> <input id="id_subject" type="text" name="subject" maxlength="100" /></p>\n<p><label for="id_message">Message:</label> <input type="text" name="message" id="id_message" /></p>\n<p><label for="id_sender">Sender:</label> <input type="text" name="sender" id="id_sender" /></p>\n<p><label for="id_cc_myself">Cc myself:</label> <input type="checkbox" name="cc_myself" id="id_cc_myself" /></p>'
>>> print f.as_p()
<p><label for="id_subject">Subject:</label> <input id="id_subject" type="text" name="subject" maxlength="100" /></p>
<p><label for="id_message">Message:</label> <input type="text" name="message" id="id_message" /></p>
<p><label for="id_sender">Sender:</label> <input type="text" name="sender" id="id_sender" /></p>
<p><label for="id_cc_myself">Cc myself:</label> <input type="checkbox" name="cc_myself" id="id_cc_myself" /></p>
``as_ul()``
~~~~~~~~~~~
``Form.as_ul()`` renders the form as a series of ``<li>`` tags, with each
``<li>`` containing one field. It does *not* include the ``<ul>`` or ``</ul>``,
so that you can specify any HTML attributes on the ``<ul>`` for flexibility::
>>> f = ContactForm()
>>> f.as_ul()
u'<li><label for="id_subject">Subject:</label> <input id="id_subject" type="text" name="subject" maxlength="100" /></li>\n<li><label for="id_message">Message:</label> <input type="text" name="message" id="id_message" /></li>\n<li><label for="id_sender">Sender:</label> <input type="text" name="sender" id="id_sender" /></li>\n<li><label for="id_cc_myself">Cc myself:</label> <input type="checkbox" name="cc_myself" id="id_cc_myself" /></li>'
>>> print f.as_ul()
<li><label for="id_subject">Subject:</label> <input id="id_subject" type="text" name="subject" maxlength="100" /></li>
<li><label for="id_message">Message:</label> <input type="text" name="message" id="id_message" /></li>
<li><label for="id_sender">Sender:</label> <input type="text" name="sender" id="id_sender" /></li>
<li><label for="id_cc_myself">Cc myself:</label> <input type="checkbox" name="cc_myself" id="id_cc_myself" /></li>
``as_table()``
~~~~~~~~~~~~~~
Finally, ``Form.as_table()`` outputs the form as an HTML ``<table>``. This is
exactly the same as ``print``. In fact, when you ``print`` a form object, it
calls its ``as_table()`` method behind the scenes::
>>> f = ContactForm()
>>> f.as_table()
u'<tr><td><label for="id_subject">Subject:</label></td><td><input id="id_subject" type="text" name="subject" maxlength="100" /></td></tr>\n<tr><td><label for="id_message">Message:</label></td><td><input type="text" name="message" id="id_message" /></td></tr>\n<tr><td><label for="id_sender">Sender:</label></td><td><input type="text" name="sender" id="id_sender" /></td></tr>\n<tr><td><label for="id_cc_myself">Cc myself:</label></td><td><input type="checkbox" name="cc_myself" id="id_cc_myself" /></td></tr>'
>>> print f.as_table()
<tr><td><label for="id_subject">Subject:</label></td><td><input id="id_subject" type="text" name="subject" maxlength="100" /></td></tr>
<tr><td><label for="id_message">Message:</label></td><td><input type="text" name="message" id="id_message" /></td></tr>
<tr><td><label for="id_sender">Sender:</label></td><td><input type="text" name="sender" id="id_sender" /></td></tr>
<tr><td><label for="id_cc_myself">Cc myself:</label></td><td><input type="checkbox" name="cc_myself" id="id_cc_myself" /></td></tr>
Configuring HTML ``<label>`` tags
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
An HTML ``<label>`` tag designates which label text is associated with which
form element. This small enhancement makes forms more usable and more accessible
to assistive devices. It's always a good idea to use ``<label>`` tags.
By default, the form rendering methods include HTML ``id`` attributes on the
form elements and corresponding ``<label>`` tags around the labels. The ``id``
attribute values are generated by prepending ``id_`` to the form field names.
This behavior is configurable, though, if you want to change the ``id``
convention or remove HTML ``id`` attributes and ``<label>`` tags entirely.
Use the ``auto_id`` argument to the ``Form`` constructor to control the label
and ``id`` behavior. This argument must be ``True``, ``False`` or a string.
If ``auto_id`` is ``False``, then the form output will not include ``<label>``
tags nor ``id`` attributes::
>>> f = ContactForm(auto_id=False)
>>> print f.as_table()
<tr><td>Subject:</td><td><input type="text" name="subject" maxlength="100" /></td></tr>
<tr><td>Message:</td><td><input type="text" name="message" /></td></tr>
<tr><td>Sender:</td><td><input type="text" name="sender" /></td></tr>
<tr><td>Cc myself:</td><td><input type="checkbox" name="cc_myself" /></td></tr>
>>> print f.as_ul()
<li>Subject: <input type="text" name="subject" maxlength="100" /></li>
<li>Message: <input type="text" name="message" /></li>
<li>Sender: <input type="text" name="sender" /></li>
<li>Cc myself: <input type="checkbox" name="cc_myself" /></li>
>>> print f.as_p()
<p>Subject: <input type="text" name="subject" maxlength="100" /></p>
<p>Message: <input type="text" name="message" /></p>
<p>Sender: <input type="text" name="sender" /></p>
<p>Cc myself: <input type="checkbox" name="cc_myself" /></p>
If ``auto_id`` is set to ``True``, then the form output *will* include
``<label>`` tags and will simply use the field name as its ``id`` for each form
field::
>>> f = ContactForm(auto_id=True)
>>> print f.as_table()
<tr><td><label for="subject">Subject:</label></td><td><input id="subject" type="text" name="subject" maxlength="100" /></td></tr>
<tr><td><label for="message">Message:</label></td><td><input type="text" name="message" id="message" /></td></tr>
<tr><td><label for="sender">Sender:</label></td><td><input type="text" name="sender" id="sender" /></td></tr>
<tr><td><label for="cc_myself">Cc myself:</label></td><td><input type="checkbox" name="cc_myself" id="cc_myself" /></td></tr>
>>> print f.as_ul()
<li><label for="subject">Subject:</label> <input id="subject" type="text" name="subject" maxlength="100" /></li>
<li><label for="message">Message:</label> <input type="text" name="message" id="message" /></li>
<li><label for="sender">Sender:</label> <input type="text" name="sender" id="sender" /></li>
<li><label for="cc_myself">Cc myself:</label> <input type="checkbox" name="cc_myself" id="cc_myself" /></li>
>>> print f.as_p()
<p><label for="subject">Subject:</label> <input id="subject" type="text" name="subject" maxlength="100" /></p>
<p><label for="message">Message:</label> <input type="text" name="message" id="message" /></p>
<p><label for="sender">Sender:</label> <input type="text" name="sender" id="sender" /></p>
<p><label for="cc_myself">Cc myself:</label> <input type="checkbox" name="cc_myself" id="cc_myself" /></p>
If ``auto_id`` is set to a string containing the format character ``'%s'``,
then the form output will include ``<label>`` tags, and will generate ``id``
attributes based on the format string. For example, for a format string
``'field_%s'``, a field named ``subject`` will get the ``id``
``'field_subject'``. Continuing our example::
>>> f = ContactForm(auto_id='id_for_%s')
>>> print f.as_table()
<tr><td><label for="id_for_subject">Subject:</label></td><td><input id="id_for_subject" type="text" name="subject" maxlength="100" /></td></tr>
<tr><td><label for="id_for_message">Message:</label></td><td><input type="text" name="message" id="id_for_message" /></td></tr>
<tr><td><label for="id_for_sender">Sender:</label></td><td><input type="text" name="sender" id="id_for_sender" /></td></tr>
<tr><td><label for="id_for_cc_myself">Cc myself:</label></td><td><input type="checkbox" name="cc_myself" id="id_for_cc_myself" /></td></tr>
>>> print f.as_ul()
<li><label for="id_for_subject">Subject:</label> <input id="id_for_subject" type="text" name="subject" maxlength="100" /></li>
<li><label for="id_for_message">Message:</label> <input type="text" name="message" id="id_for_message" /></li>
<li><label for="id_for_sender">Sender:</label> <input type="text" name="sender" id="id_for_sender" /></li>
<li><label for="id_for_cc_myself">Cc myself:</label> <input type="checkbox" name="cc_myself" id="id_for_cc_myself" /></li>
>>> print f.as_p()
<p><label for="id_for_subject">Subject:</label> <input id="id_for_subject" type="text" name="subject" maxlength="100" /></p>
<p><label for="id_for_message">Message:</label> <input type="text" name="message" id="id_for_message" /></p>
<p><label for="id_for_sender">Sender:</label> <input type="text" name="sender" id="id_for_sender" /></p>
<p><label for="id_for_cc_myself">Cc myself:</label> <input type="checkbox" name="cc_myself" id="id_for_cc_myself" /></p>
If ``auto_id`` is set to any other true value -- such as a string that doesn't
include ``%s`` -- then the library will act as if ``auto_id`` is ``True``.
By default, ``auto_id`` is set to the string ``'id_%s'``.
More coming soon
================
That's all the documentation for now. For more, see the file
http://code.djangoproject.com/browser/django/trunk/tests/regressiontests/forms/tests.py
-- the unit tests for ``django.newforms``. This can give you a good idea of
what's possible.
Using forms to validate data
----------------------------
Using forms with templates
==========================
Using forms in views
====================