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834 lines
38 KiB
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834 lines
38 KiB
Plaintext
====================
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The newforms library
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====================
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``django.newforms`` is Django's fantastic new form-handling library. It's a
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replacement for ``django.forms``, the old form/manipulator/validation
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framework. This document explains how to use this new library.
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Migration plan
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==============
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``django.newforms`` currently is only available in the Django development version
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-- i.e., it's not available in the Django 0.95 release. For the next Django
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release, our plan is to do the following:
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* As of revision [4208], we've copied the current ``django.forms`` to
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``django.oldforms``. This allows you to upgrade your code *now* rather
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than waiting for the backwards-incompatible change and rushing to fix
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your code after the fact. Just change your import statements like this::
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from django import forms # old
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from django import oldforms as forms # new
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* At an undecided future date, we will move the current ``django.newforms``
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to ``django.forms``. This will be a backwards-incompatible change, and
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anybody who is still using the old version of ``django.forms`` at that
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time will need to change their import statements, as described in the
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previous bullet.
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* We will remove ``django.oldforms`` in the release *after* the next Django
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release -- the release that comes after the release in which we're
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creating the new ``django.forms``.
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With this in mind, we recommend you use the following import statement when
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using ``django.newforms``::
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from django import newforms as forms
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This way, your code can refer to the ``forms`` module, and when
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``django.newforms`` is renamed to ``django.forms``, you'll only have to change
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your ``import`` statements.
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If you prefer "``import *``" syntax, you can do the following::
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from django.newforms import *
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This will import all fields, widgets, form classes and other various utilities
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into your local namespace. Some people find this convenient; others find it
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too messy. The choice is yours.
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Overview
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========
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As with the ``django.forms`` ("manipulators") system before it, ``django.newforms``
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is intended to handle HTML form display, validation and redisplay. It's what
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you use if you want to perform server-side validation for an HTML form.
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For example, if your Web site has a contact form that visitors can use to
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send you e-mail, you'd use this library to implement the display of the HTML
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form fields, along with the form validation. Any time you need to use an HTML
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``<form>``, you can use this library.
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The library deals with these concepts:
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* **Widget** -- A class that corresponds to an HTML form widget, e.g.
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``<input type="text">`` or ``<textarea>``. This handles rendering of the
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widget as HTML.
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* **Field** -- A class that is responsible for doing validation, e.g.
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an ``EmailField`` that makes sure its data is a valid e-mail address.
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* **Form** -- A collection of fields that knows how to validate itself and
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display itself as HTML.
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The library is decoupled from the other Django components, such as the database
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layer, views and templates. It relies only on Django settings, a couple of
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``django.utils`` helper functions and Django's internationalization hooks (but
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you're not required to be using internationalization features to use this
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library).
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Form objects
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============
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The primary way of using the ``newforms`` library is to create a form object.
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Do this by subclassing ``django.newforms.Form`` and specifying the form's
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fields, in a declarative style that you'll be familiar with if you've used
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Django database models. In this section, we'll iteratively develop a form
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object that you might use to implement "contact me" functionality on your
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personal Web site.
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Start with this basic ``Form`` subclass, which we'll call ``ContactForm``::
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from django import newforms as forms
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class ContactForm(forms.Form):
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subject = forms.CharField(max_length=100)
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message = forms.CharField()
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sender = forms.EmailField()
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cc_myself = forms.BooleanField()
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A form is composed of ``Field`` objects. In this case, our form has four
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fields: ``subject``, ``message``, ``sender`` and ``cc_myself``. We'll explain
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the different types of fields -- e.g., ``CharField`` and ``EmailField`` --
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shortly.
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Creating ``Form`` instances
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---------------------------
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A ``Form`` instance is either **bound** or **unbound** to a set of data.
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* If it's **bound** to a set of data, it's capable of validating that data
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and rendering the form as HTML with the data displayed in the HTML.
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* If it's **unbound**, it cannot do validation (because there's no data to
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validate!), but it can still render the blank form as HTML.
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To create an unbound ``Form`` instance, simply instantiate the class::
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>>> f = ContactForm()
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To bind data to a form, pass the data as a dictionary as the first parameter to
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your ``Form`` class constructor::
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>>> data = {'subject': 'hello',
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... 'message': 'Hi there',
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... 'sender': 'foo@example.com',
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... 'cc_myself': True}
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>>> f = ContactForm(data)
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In this dictionary, the keys are the field names, which correspond to the
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attributes in your ``Form`` class. The values are the data you're trying
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to validate. These will usually be strings, but there's no requirement that
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they be strings; the type of data you pass depends on the ``Field``, as we'll
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see in a moment.
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If you need to distinguish between bound and unbound form instances at runtime,
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check the value of the form's ``is_bound`` attribute::
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>>> f = ContactForm()
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>>> f.is_bound
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False
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>>> f = ContactForm({'subject': 'hello'})
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>>> f.is_bound
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True
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Note that passing an empty dictionary creates a *bound* form with empty data::
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>>> f = ContactForm({})
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>>> f.is_bound
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True
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If you have a bound ``Form`` instance and want to change the data somehow, or
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if you want to bind an unbound ``Form`` instance to some data, create another
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``Form`` instance. There is no way to change data in a ``Form`` instance. Once
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a ``Form`` instance has been created, you should consider its data immutable,
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whether it has data or not.
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Using forms to validate data
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----------------------------
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The primary task of a ``Form`` object is to validate data. With a bound
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``Form`` instance, call the ``is_valid()`` method to run validation and return
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a boolean designating whether the data was valid::
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>>> data = {'subject': 'hello',
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... 'message': 'Hi there',
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... 'sender': 'foo@example.com',
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... 'cc_myself': True}
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>>> f = ContactForm(data)
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>>> f.is_valid()
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True
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Let's try with some invalid data. In this case, ``subject`` is blank (an error,
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because all fields are required by default) and ``sender`` is not a valid
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e-mail address::
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>>> data = {'subject': '',
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... 'message': 'Hi there',
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... 'sender': 'invalid e-mail address',
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... 'cc_myself': True}
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>>> f = ContactForm(data)
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>>> f.is_valid()
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False
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Access the ``Form`` attribute ``errors`` to get a dictionary of error messages::
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>>> f.errors
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{'sender': [u'Enter a valid e-mail address.'], 'subject': [u'This field is required.']}
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In this dictionary, the keys are the field names, and the values are lists of
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Unicode strings representing the error messages. The error messages are stored
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in lists because a field can have multiple error messages.
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You can access ``errors`` without having to call ``is_valid()`` first. The
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form's data will be validated the first time either you call ``is_valid()`` or
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access ``errors``.
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Behavior of unbound forms
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~~~~~~~~~~~~~~~~~~~~~~~~~
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It's meaningless to validate a form with no data, but, for the record, here's
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what happens with unbound forms::
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>>> f = ContactForm()
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>>> f.is_valid()
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False
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>>> f.errors
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{}
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Accessing "clean" data
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----------------------
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Each ``Field`` in a ``Form`` class is responsible not only for validating data,
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but also for "cleaning" it -- normalizing it to a consistent format. This is a
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nice feature, because it allows data for a particular field to be input in
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a variety of ways, always resulting in consistent output.
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For example, ``DateField`` normalizes input into a Python ``datetime.date``
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object. Regardless of whether you pass it a string in the format
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``'1994-07-15'``, a ``datetime.date`` object or a number of other formats,
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``DateField`` will always normalize it to a ``datetime.date`` object as long as
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it's valid.
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Once you've created a ``Form`` instance with a set of data and validated it,
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you can access the clean data via the ``clean_data`` attribute of the ``Form``
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object::
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>>> data = {'subject': 'hello',
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... 'message': 'Hi there',
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... 'sender': 'foo@example.com',
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... 'cc_myself': True}
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>>> f = ContactForm(data)
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>>> f.is_valid()
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True
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>>> f.clean_data
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{'cc_myself': True, 'message': u'Hi there', 'sender': u'foo@example.com', 'subject': u'hello'}
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Note that any text-based field -- such as ``CharField`` or ``EmailField`` --
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always cleans the input into a Unicode string. We'll cover the encoding
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implications later in this document.
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If your data does *not* validate, your ``Form`` instance will not have a
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``clean_data`` attribute::
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>>> data = {'subject': '',
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... 'message': 'Hi there',
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... 'sender': 'invalid e-mail address',
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... 'cc_myself': True}
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>>> f = ContactForm(data)
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>>> f.is_valid()
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False
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>>> f.clean_data
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Traceback (most recent call last):
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...
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AttributeError: 'ContactForm' object has no attribute 'clean_data'
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``clean_data`` will always *only* contain a key for fields defined in the
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``Form``, even if you pass extra data when you define the ``Form``. In this
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example, we pass a bunch of extra fields to the ``ContactForm`` constructor,
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but ``clean_data`` contains only the form's fields::
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>>> data = {'subject': 'hello',
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... 'message': 'Hi there',
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... 'sender': 'foo@example.com',
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... 'cc_myself': True,
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... 'extra_field_1': 'foo',
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... 'extra_field_2': 'bar',
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... 'extra_field_3': 'baz'}
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>>> f = ContactForm(data)
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>>> f.is_valid()
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True
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>>> f.clean_data # Doesn't contain extra_field_1, etc.
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{'cc_myself': True, 'message': u'Hi there', 'sender': u'foo@example.com', 'subject': u'hello'}
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Behavior of unbound forms
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~~~~~~~~~~~~~~~~~~~~~~~~~
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It's meaningless to request "clean" data in a form with no data, but, for the
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record, here's what happens with unbound forms::
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>>> f = ContactForm()
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>>> f.clean_data
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Traceback (most recent call last):
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...
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AttributeError: 'ContactForm' object has no attribute 'clean_data'
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Outputting forms as HTML
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------------------------
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The second task of a ``Form`` object is to render itself as HTML. To do so,
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simply ``print`` it::
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>>> f = ContactForm()
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>>> print f
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<tr><th><label for="id_subject">Subject:</label></th><td><input id="id_subject" type="text" name="subject" maxlength="100" /></td></tr>
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<tr><th><label for="id_message">Message:</label></th><td><input type="text" name="message" id="id_message" /></td></tr>
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<tr><th><label for="id_sender">Sender:</label></th><td><input type="text" name="sender" id="id_sender" /></td></tr>
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<tr><th><label for="id_cc_myself">Cc myself:</label></th><td><input type="checkbox" name="cc_myself" id="id_cc_myself" /></td></tr>
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If the form is bound to data, the HTML output will include that data
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appropriately. For example, if a field is represented by an
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``<input type="text">``, the data will be in the ``value`` attribute. If a
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field is represented by an ``<input type="checkbox">``, then that HTML will
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include ``checked="checked"`` if appropriate::
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>>> data = {'subject': 'hello',
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... 'message': 'Hi there',
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... 'sender': 'foo@example.com',
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... 'cc_myself': True}
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>>> f = ContactForm(data)
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>>> print f
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<tr><th><label for="id_subject">Subject:</label></th><td><input id="id_subject" type="text" name="subject" maxlength="100" value="hello" /></td></tr>
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<tr><th><label for="id_message">Message:</label></th><td><input type="text" name="message" id="id_message" value="Hi there" /></td></tr>
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<tr><th><label for="id_sender">Sender:</label></th><td><input type="text" name="sender" id="id_sender" value="foo@example.com" /></td></tr>
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<tr><th><label for="id_cc_myself">Cc myself:</label></th><td><input type="checkbox" name="cc_myself" id="id_cc_myself" checked="checked" /></td></tr>
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This default output is a two-column HTML table, with a ``<tr>`` for each field.
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Notice the following:
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* For flexibility, the output does *not* include the ``<table>`` and
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``</table>`` tags, nor does it include the ``<form>`` and ``</form>``
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tags or an ``<input type="submit">`` tag. It's your job to do that.
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* Each field type has a default HTML representation. ``CharField`` and
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``EmailField`` are represented by an ``<input type="text">``.
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``BooleanField`` is represented by an ``<input type="checkbox">``. Note
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these are merely sensible defaults; you can specify which HTML to use for
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a given field by using widgets, which we'll explain shortly.
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* The HTML ``name`` for each tag is taken directly from its attribute name
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in the ``ContactForm`` class.
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* The text label for each field -- e.g. ``'Subject:'``, ``'Message:'`` and
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``'Cc myself:'`` is generated from the field name by converting all
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underscores to spaces and upper-casing the first letter. Again, note
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these are merely sensible defaults; you can also specify labels manually.
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* Each text label is surrounded in an HTML ``<label>`` tag, which points
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to the appropriate form field via its ``id``. Its ``id``, in turn, is
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generated by prepending ``'id_'`` to the field name. The ``id``
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attributes and ``<label>`` tags are included in the output by default, to
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follow best practices, but you can change that behavior.
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Although ``<table>`` output is the default output style when you ``print`` a
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form, other output styles are available. Each style is available as a method on
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a form object, and each rendering method returns a Unicode object.
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``as_p()``
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~~~~~~~~~~
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``Form.as_p()`` renders the form as a series of ``<p>`` tags, with each ``<p>``
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containing one field::
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>>> f = ContactForm()
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>>> f.as_p()
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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>'
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>>> print f.as_p()
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<p><label for="id_subject">Subject:</label> <input id="id_subject" type="text" name="subject" maxlength="100" /></p>
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<p><label for="id_message">Message:</label> <input type="text" name="message" id="id_message" /></p>
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<p><label for="id_sender">Sender:</label> <input type="text" name="sender" id="id_sender" /></p>
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<p><label for="id_cc_myself">Cc myself:</label> <input type="checkbox" name="cc_myself" id="id_cc_myself" /></p>
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``as_ul()``
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~~~~~~~~~~~
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``Form.as_ul()`` renders the form as a series of ``<li>`` tags, with each
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``<li>`` containing one field. It does *not* include the ``<ul>`` or ``</ul>``,
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so that you can specify any HTML attributes on the ``<ul>`` for flexibility::
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>>> f = ContactForm()
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>>> f.as_ul()
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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>'
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>>> print f.as_ul()
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<li><label for="id_subject">Subject:</label> <input id="id_subject" type="text" name="subject" maxlength="100" /></li>
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<li><label for="id_message">Message:</label> <input type="text" name="message" id="id_message" /></li>
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<li><label for="id_sender">Sender:</label> <input type="text" name="sender" id="id_sender" /></li>
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<li><label for="id_cc_myself">Cc myself:</label> <input type="checkbox" name="cc_myself" id="id_cc_myself" /></li>
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``as_table()``
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~~~~~~~~~~~~~~
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Finally, ``Form.as_table()`` outputs the form as an HTML ``<table>``. This is
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exactly the same as ``print``. In fact, when you ``print`` a form object, it
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calls its ``as_table()`` method behind the scenes::
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>>> f = ContactForm()
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>>> f.as_table()
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u'<tr><th><label for="id_subject">Subject:</label></th><td><input id="id_subject" type="text" name="subject" maxlength="100" /></td></tr>\n<tr><th><label for="id_message">Message:</label></th><td><input type="text" name="message" id="id_message" /></td></tr>\n<tr><th><label for="id_sender">Sender:</label></th><td><input type="text" name="sender" id="id_sender" /></td></tr>\n<tr><th><label for="id_cc_myself">Cc myself:</label></th><td><input type="checkbox" name="cc_myself" id="id_cc_myself" /></td></tr>'
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>>> print f.as_table()
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<tr><th><label for="id_subject">Subject:</label></th><td><input id="id_subject" type="text" name="subject" maxlength="100" /></td></tr>
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<tr><th><label for="id_message">Message:</label></th><td><input type="text" name="message" id="id_message" /></td></tr>
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<tr><th><label for="id_sender">Sender:</label></th><td><input type="text" name="sender" id="id_sender" /></td></tr>
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<tr><th><label for="id_cc_myself">Cc myself:</label></th><td><input type="checkbox" name="cc_myself" id="id_cc_myself" /></td></tr>
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Configuring HTML ``<label>`` tags
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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An HTML ``<label>`` tag designates which label text is associated with which
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form element. This small enhancement makes forms more usable and more accessible
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to assistive devices. It's always a good idea to use ``<label>`` tags.
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By default, the form rendering methods include HTML ``id`` attributes on the
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form elements and corresponding ``<label>`` tags around the labels. The ``id``
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attribute values are generated by prepending ``id_`` to the form field names.
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This behavior is configurable, though, if you want to change the ``id``
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convention or remove HTML ``id`` attributes and ``<label>`` tags entirely.
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Use the ``auto_id`` argument to the ``Form`` constructor to control the label
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and ``id`` behavior. This argument must be ``True``, ``False`` or a string.
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If ``auto_id`` is ``False``, then the form output will not include ``<label>``
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tags nor ``id`` attributes::
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>>> f = ContactForm(auto_id=False)
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>>> print f.as_table()
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<tr><th>Subject:</th><td><input type="text" name="subject" maxlength="100" /></td></tr>
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<tr><th>Message:</th><td><input type="text" name="message" /></td></tr>
|
|
<tr><th>Sender:</th><td><input type="text" name="sender" /></td></tr>
|
|
<tr><th>Cc myself:</th><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><th><label for="subject">Subject:</label></th><td><input id="subject" type="text" name="subject" maxlength="100" /></td></tr>
|
|
<tr><th><label for="message">Message:</label></th><td><input type="text" name="message" id="message" /></td></tr>
|
|
<tr><th><label for="sender">Sender:</label></th><td><input type="text" name="sender" id="sender" /></td></tr>
|
|
<tr><th><label for="cc_myself">Cc myself:</label></th><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><th><label for="id_for_subject">Subject:</label></th><td><input id="id_for_subject" type="text" name="subject" maxlength="100" /></td></tr>
|
|
<tr><th><label for="id_for_message">Message:</label></th><td><input type="text" name="message" id="id_for_message" /></td></tr>
|
|
<tr><th><label for="id_for_sender">Sender:</label></th><td><input type="text" name="sender" id="id_for_sender" /></td></tr>
|
|
<tr><th><label for="id_for_cc_myself">Cc myself:</label></th><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'``.
|
|
|
|
Notes on field ordering
|
|
~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
In the ``as_p()``, ``as_ul()`` and ``as_table()`` shortcuts, the fields are
|
|
displayed in the order in which you define them in your form class. For
|
|
example, in the ``ContactForm`` example, the fields are defined in the order
|
|
``subject``, ``message``, ``sender``, ``cc_myself``. To reorder the HTML
|
|
output, just change the order in which those fields are listed in the class.
|
|
|
|
How errors are displayed
|
|
~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
If you render a bound ``Form`` object, the act of rendering will automatically
|
|
run the form's validation if it hasn't already happened, and the HTML output
|
|
will include the validation errors as a ``<ul>`` near the field. The particular
|
|
positioning of the error messages depends on the output method you're using::
|
|
|
|
>>> data = {'subject': '',
|
|
... 'message': 'Hi there',
|
|
... 'sender': 'invalid e-mail address',
|
|
... 'cc_myself': True}
|
|
>>> f = ContactForm(data, auto_id=False)
|
|
>>> print f.as_table()
|
|
<tr><th>Subject:</th><td><ul class="errorlist"><li>This field is required.</li></ul><input type="text" name="subject" maxlength="100" /></td></tr>
|
|
<tr><th>Message:</th><td><input type="text" name="message" value="Hi there" /></td></tr>
|
|
<tr><th>Sender:</th><td><ul class="errorlist"><li>Enter a valid e-mail address.</li></ul><input type="text" name="sender" value="invalid e-mail address" /></td></tr>
|
|
<tr><th>Cc myself:</th><td><input checked="checked" type="checkbox" name="cc_myself" /></td></tr>
|
|
>>> print f.as_ul()
|
|
<li><ul class="errorlist"><li>This field is required.</li></ul>Subject: <input type="text" name="subject" maxlength="100" /></li>
|
|
<li>Message: <input type="text" name="message" value="Hi there" /></li>
|
|
<li><ul class="errorlist"><li>Enter a valid e-mail address.</li></ul>Sender: <input type="text" name="sender" value="invalid e-mail address" /></li>
|
|
<li>Cc myself: <input checked="checked" type="checkbox" name="cc_myself" /></li>
|
|
>>> print f.as_p()
|
|
<p><ul class="errorlist"><li>This field is required.</li></ul></p>
|
|
<p>Subject: <input type="text" name="subject" maxlength="100" /></p>
|
|
<p>Message: <input type="text" name="message" value="Hi there" /></p>
|
|
<p><ul class="errorlist"><li>Enter a valid e-mail address.</li></ul></p>
|
|
<p>Sender: <input type="text" name="sender" value="invalid e-mail address" /></p>
|
|
<p>Cc myself: <input checked="checked" type="checkbox" name="cc_myself" /></p>
|
|
|
|
More granular output
|
|
~~~~~~~~~~~~~~~~~~~~
|
|
|
|
The ``as_p()``, ``as_ul()`` and ``as_table()`` methods are simply shortcuts for
|
|
lazy developers -- they're not the only way a form object can be displayed.
|
|
|
|
To display the HTML for a single field in your form, use dictionary lookup
|
|
syntax using the field's name as the key, and print the resulting object::
|
|
|
|
>>> f = ContactForm()
|
|
>>> print f['subject']
|
|
<input id="id_subject" type="text" name="subject" maxlength="100" />
|
|
>>> print f['message']
|
|
<input type="text" name="message" id="id_message" />
|
|
>>> print f['sender']
|
|
<input type="text" name="sender" id="id_sender" />
|
|
>>> print f['cc_myself']
|
|
<input type="checkbox" name="cc_myself" id="id_cc_myself" />
|
|
|
|
Call ``str()`` or ``unicode()`` on the field to get its rendered HTML as a
|
|
string or Unicode object, respectively::
|
|
|
|
>>> str(f['subject'])
|
|
'<input id="id_subject" type="text" name="subject" maxlength="100" />'
|
|
>>> unicode(f['subject'])
|
|
u'<input id="id_subject" type="text" name="subject" maxlength="100" />'
|
|
|
|
The field-specific output honors the form object's ``auto_id`` setting::
|
|
|
|
>>> f = ContactForm(auto_id=False)
|
|
>>> print f['message']
|
|
<input type="text" name="message" />
|
|
>>> f = ContactForm(auto_id='id_%s')
|
|
>>> print f['message']
|
|
<input type="text" name="message" id="id_message" />
|
|
|
|
For a field's list of errors, access the field's ``errors`` attribute. This
|
|
is a list-like object that is displayed as an HTML ``<ul>`` when printed::
|
|
|
|
>>> data = {'subject': 'hi', 'message': '', 'sender': '', 'cc_myself': ''}
|
|
>>> f = ContactForm(data, auto_id=False)
|
|
>>> print f['message']
|
|
<input type="text" name="message" />
|
|
>>> f['message'].errors
|
|
[u'This field is required.']
|
|
>>> print f['message'].errors
|
|
<ul class="errorlist"><li>This field is required.</li></ul>
|
|
>>> f['subject'].errors
|
|
[]
|
|
>>> print f['subject'].errors
|
|
|
|
>>> str(f['subject'].errors)
|
|
''
|
|
|
|
Fields
|
|
======
|
|
|
|
When you create a ``Form`` class, the most important part is defining the
|
|
fields of the form. Each field has custom validation logic, along with a few
|
|
other hooks.
|
|
|
|
Although the primary way you'll use ``Field`` classes is in ``Form`` classes,
|
|
you can also instantiate them and use them directly to get a better idea of
|
|
how they work. Each ``Field`` instance has a ``clean()`` method, which takes
|
|
a single argument and either raises a ``django.newforms.ValidationError``
|
|
exception or returns the clean value::
|
|
|
|
>>> f = forms.EmailField()
|
|
>>> f.clean('foo@example.com')
|
|
u'foo@example.com'
|
|
>>> f.clean(u'foo@example.com')
|
|
u'foo@example.com'
|
|
>>> f.clean('invalid e-mail address')
|
|
Traceback (most recent call last):
|
|
...
|
|
ValidationError: [u'Enter a valid e-mail address.']
|
|
|
|
If you've used Django's old forms/validation framework, take care in noticing
|
|
this ``ValidationError`` is different than the previous ``ValidationError``.
|
|
This one lives at ``django.newforms.ValidationError`` rather than
|
|
``django.core.validators.ValidationError``.
|
|
|
|
Core field arguments
|
|
--------------------
|
|
|
|
Each ``Field`` class constructor takes at least these arguments. Some
|
|
``Field`` classes take additional, field-specific arguments, but the following
|
|
should *always* be available:
|
|
|
|
``required``
|
|
~~~~~~~~~~~~
|
|
|
|
By default, each ``Field`` class assumes the value is required, so if you pass
|
|
an empty value -- either ``None`` or the empty string (``""``) -- then
|
|
``clean()`` will raise a ``ValidationError`` exception::
|
|
|
|
>>> f = forms.CharField()
|
|
>>> f.clean('foo')
|
|
u'foo'
|
|
>>> f.clean('')
|
|
Traceback (most recent call last):
|
|
...
|
|
ValidationError: [u'This field is required.']
|
|
>>> f.clean(None)
|
|
Traceback (most recent call last):
|
|
...
|
|
ValidationError: [u'This field is required.']
|
|
>>> f.clean(' ')
|
|
u' '
|
|
>>> f.clean(0)
|
|
u'0'
|
|
>>> f.clean(True)
|
|
u'True'
|
|
>>> f.clean(False)
|
|
u'False'
|
|
|
|
To specify that a field is *not* required, pass ``required=False`` to the
|
|
``Field`` constructor::
|
|
|
|
>>> f = forms.CharField(required=False)
|
|
>>> f.clean('foo')
|
|
u'foo'
|
|
>>> f.clean('')
|
|
u''
|
|
>>> f.clean(None)
|
|
u''
|
|
>>> f.clean(0)
|
|
u'0'
|
|
>>> f.clean(True)
|
|
u'True'
|
|
>>> f.clean(False)
|
|
u'False'
|
|
|
|
If a ``Field`` has ``required=False`` and you pass ``clean()`` an empty value,
|
|
then ``clean()`` will return a *normalized* empty value rather than raising
|
|
``ValidationError``. For ``CharField``, this will be a Unicode empty string.
|
|
For other ``Field`` classes, it might be ``None``. (This varies from field to
|
|
field.)
|
|
|
|
``label``
|
|
~~~~~~~~~
|
|
|
|
The ``label`` argument lets you specify the "human-friendly" label for this
|
|
field. This is used when the ``Field`` is displayed in a ``Form``.
|
|
|
|
As explained in _`Outputting forms as HTML` above, the default label for a
|
|
``Field`` is generated from the field name by converting all underscores to
|
|
spaces and upper-casing the first letter. Specify ``label`` if that default
|
|
behavior doesn't result in an adequate label.
|
|
|
|
Here's a full example ``Form`` that implements ``label`` for two of its fields.
|
|
We've specified ``auto_id=False`` to simplify the output::
|
|
|
|
>>> class CommentForm(forms.Form):
|
|
... name = forms.CharField(label='Your name')
|
|
... url = forms.URLField(label='Your Web site', required=False)
|
|
... comment = forms.CharField()
|
|
>>> f = CommentForm(auto_id=False)
|
|
>>> print f
|
|
<tr><th>Your name:</th><td><input type="text" name="name" /></td></tr>
|
|
<tr><th>Your Web site:</th><td><input type="text" name="url" /></td></tr>
|
|
<tr><th>Comment:</th><td><input type="text" name="comment" /></td></tr>
|
|
|
|
``initial``
|
|
~~~~~~~~~~~
|
|
|
|
The ``initial`` argument lets you specify the initial value to use when
|
|
rendering this ``Field`` in an unbound ``Form``.
|
|
|
|
The use-case for this is when you want to display an "empty" form in which a
|
|
field is initialized to a particular value. For example::
|
|
|
|
>>> class CommentForm(forms.Form):
|
|
... name = forms.CharField(initial='Your name')
|
|
... url = forms.URLField(initial='http://')
|
|
... comment = forms.CharField()
|
|
>>> f = CommentForm(auto_id=False)
|
|
>>> print f
|
|
<tr><th>Name:</th><td><input type="text" name="name" value="Your name" /></td></tr>
|
|
<tr><th>Url:</th><td><input type="text" name="url" value="http://" /></td></tr>
|
|
<tr><th>Comment:</th><td><input type="text" name="comment" /></td></tr>
|
|
|
|
You may be thinking, why not just pass a dictionary of the initial values as
|
|
data when displaying the form? Well, if you do that, you'll trigger validation,
|
|
and the HTML output will include any validation errors::
|
|
|
|
>>> class CommentForm(forms.Form):
|
|
... name = forms.CharField()
|
|
... url = forms.URLField()
|
|
... comment = forms.CharField()
|
|
>>> default_data = {'name': 'Your name', 'url': 'http://'}
|
|
>>> f = CommentForm(default_data, auto_id=False)
|
|
>>> print f
|
|
<tr><th>Name:</th><td><input type="text" name="name" value="Your name" /></td></tr>
|
|
<tr><th>Url:</th><td><ul class="errorlist"><li>Enter a valid URL.</li></ul><input type="text" name="url" value="http://" /></td></tr>
|
|
<tr><th>Comment:</th><td><ul class="errorlist"><li>This field is required.</li></ul><input type="text" name="comment" /></td></tr>
|
|
|
|
This is why ``initial`` values are only displayed for unbound forms. For bound
|
|
forms, the HTML output will use the bound data.
|
|
|
|
Also note that ``initial`` values are *not* used as "fallback" data in
|
|
validation if a particular field's value is not given. ``initial`` values are
|
|
*only* intended for initial form display::
|
|
|
|
>>> class CommentForm(forms.Form):
|
|
... name = forms.CharField(initial='Your name')
|
|
... url = forms.URLField(initial='http://')
|
|
... comment = forms.CharField()
|
|
>>> data = {'name': '', 'url': '', 'comment': 'Foo'}
|
|
>>> f = CommentForm(data)
|
|
>>> f.is_valid()
|
|
False
|
|
# The form does *not* fall back to using the initial values.
|
|
>>> f.errors
|
|
{'url': [u'This field is required.'], 'name': [u'This field is required.']}
|
|
|
|
``widget``
|
|
~~~~~~~~~~
|
|
|
|
The ``widget`` argument lets you specify a ``Widget`` class to use when
|
|
rendering this ``Field``. See _`Widgets` below for more information.
|
|
|
|
``help_text``
|
|
~~~~~~~~~~~~~
|
|
|
|
The ``help_text`` argument lets you specify descriptive text for this
|
|
``Field``. If you provide ``help_text``, it will be displayed next to the
|
|
``Field`` when the ``Field`` is rendered in a ``Form``.
|
|
|
|
Here's a full example ``Form`` that implements ``help_text`` for two of its
|
|
fields. We've specified ``auto_id=False`` to simplify the output::
|
|
|
|
>>> class HelpTextContactForm(forms.Form):
|
|
... subject = forms.CharField(max_length=100, help_text='100 characters max.')
|
|
... message = forms.CharField()
|
|
... sender = forms.EmailField(help_text='A valid e-mail address, please.')
|
|
... cc_myself = forms.BooleanField()
|
|
>>> f = HelpTextContactForm(auto_id=False)
|
|
>>> print f.as_table()
|
|
<tr><th>Subject:</th><td><input type="text" name="subject" maxlength="100" /><br />100 characters max.</td></tr>
|
|
<tr><th>Message:</th><td><input type="text" name="message" /></td></tr>
|
|
<tr><th>Sender:</th><td><input type="text" name="sender" /><br />A valid e-mail address, please.</td></tr>
|
|
<tr><th>Cc myself:</th><td><input type="checkbox" name="cc_myself" /></td></tr>
|
|
>>> print f.as_ul()
|
|
<li>Subject: <input type="text" name="subject" maxlength="100" /> 100 characters max.</li>
|
|
<li>Message: <input type="text" name="message" /></li>
|
|
<li>Sender: <input type="text" name="sender" /> A valid e-mail address, please.</li>
|
|
<li>Cc myself: <input type="checkbox" name="cc_myself" /></li>
|
|
>>> print f.as_p()
|
|
<p>Subject: <input type="text" name="subject" maxlength="100" /> 100 characters max.</p>
|
|
<p>Message: <input type="text" name="message" /></p>
|
|
<p>Sender: <input type="text" name="sender" /> A valid e-mail address, please.</p>
|
|
<p>Cc myself: <input type="checkbox" name="cc_myself" /></p>
|
|
|
|
Dynamic initial values
|
|
----------------------
|
|
|
|
The ``initial`` argument to ``Field`` (explained above) lets you hard-code the
|
|
initial value for a ``Field`` -- but what if you want to declare the initial
|
|
value at runtime? For example, you might want to fill in a ``username`` field
|
|
with the username of the current session.
|
|
|
|
To accomplish this, use the ``initial`` argument to a ``Form``. This argument,
|
|
if given, should be a dictionary mapping field names to initial values. Only
|
|
include the fields for which you're specifying an initial value; it's not
|
|
necessary to include every field in your form. For example::
|
|
|
|
>>> class CommentForm(forms.Form):
|
|
... name = forms.CharField()
|
|
... url = forms.URLField()
|
|
... comment = forms.CharField()
|
|
>>> f = CommentForm(initial={'name': 'your username'}, auto_id=False)
|
|
>>> print f
|
|
<tr><th>Name:</th><td><input type="text" name="name" value="your username" /></td></tr>
|
|
<tr><th>Url:</th><td><input type="text" name="url" /></td></tr>
|
|
<tr><th>Comment:</th><td><input type="text" name="comment" /></td></tr>
|
|
>>> f = CommentForm(initial={'name': 'another username'}, auto_id=False)
|
|
>>> print f
|
|
<tr><th>Name:</th><td><input type="text" name="name" value="another username" /></td></tr>
|
|
<tr><th>Url:</th><td><input type="text" name="url" /></td></tr>
|
|
<tr><th>Comment:</th><td><input type="text" name="comment" /></td></tr>
|
|
|
|
Just like the ``initial`` parameter to ``Field``, these values are only
|
|
displayed for unbound forms, and they're not used as fallback values if a
|
|
particular value isn't provided.
|
|
|
|
Finally, note that if a ``Field`` defines ``initial`` *and* you include
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|
``initial`` when instantiating the ``Form``, then the latter ``initial`` will
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|
have precedence. In this example, ``initial`` is provided both at the field
|
|
level and at the form instance level, and the latter gets precedence::
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|
|
|
>>> class CommentForm(forms.Form):
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|
... name = forms.CharField(initial='class')
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|
... url = forms.URLField()
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|
... comment = forms.CharField()
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|
>>> f = CommentForm(initial={'name': 'instance'}, auto_id=False)
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|
>>> print f
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|
<tr><th>Name:</th><td><input type="text" name="name" value="instance" /></td></tr>
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|
<tr><th>Url:</th><td><input type="text" name="url" /></td></tr>
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|
<tr><th>Comment:</th><td><input type="text" name="comment" /></td></tr>
|
|
|
|
More coming soon
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|
================
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|
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|
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.
|
|
|
|
If you're really itching to learn and use this library, please be patient.
|
|
We're working hard on finishing both the code and documentation.
|
|
|
|
Widgets
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|
=======
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