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diff --git a/docs/newforms.txt b/docs/newforms.txt index 9bfbc75ee7..063f686ed5 100644 --- a/docs/newforms.txt +++ b/docs/newforms.txt @@ -2,9 +2,9 @@ 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. +``django.newforms`` is Django's fantastic new form-handling library. It's a +replacement for ``django.forms``, the old form/manipulator/validation +framework. This document explains how to use this new library. Migration plan ============== @@ -13,18 +13,23 @@ Migration plan -- 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:: + * As of revision [4208], we've copied the current ``django.forms`` to + ``django.oldforms``. This allows you to upgrade your code *now* rather + than waiting for the backwards-incompatible change and rushing to fix + your code after the fact. Just change your import statements like this:: from django import forms # old from django import oldforms as forms # new - * Move the current ``django.newforms`` to ``django.forms``. + * At an undecided future date, we will move the current ``django.newforms`` + to ``django.forms``. This will be a backwards-incompatible change, and + anybody who is still using the old version of ``django.forms`` at that + time will need to change their import statements, as described in the + previous bullet. * 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``. + creating the new ``django.forms``. With this in mind, we recommend you use the following import statement when using ``django.newforms``:: @@ -46,9 +51,14 @@ too messy. The choice is yours. Overview ======== -As the ``django.forms`` 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. +As with 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: @@ -62,13 +72,751 @@ The library deals with these concepts: * **Form** -- A collection of fields that knows how to validate itself and display itself as HTML. +The library is decoupled from the other Django components, such as the database +layer, views and templates. It relies only on Django settings, a couple of +``django.utils`` helper functions and Django's internationalization hooks (but +you're not required to be using internationalization features to use this +library). +Form objects +============ -Using forms with templates -========================== +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 use to implement "contact me" functionality on your +personal Web site. -Using forms in views -==================== +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. + +Creating ``Form`` instances +--------------------------- + +A ``Form`` instance is either **bound** or **unbound** to a set of data. + + * If it's **bound** to a set of data, it's capable of validating that data + and rendering the form as HTML with the data displayed in the HTML. + + * If it's **unbound**, it cannot do validation (because there's no data to + validate!), but it can still render the blank form as HTML. + +To create an unbound ``Form`` instance, simply instantiate the class:: + + >>> f = ContactForm() + +To bind data to a form, pass the data as a dictionary as the first parameter to +your ``Form`` class constructor:: + + >>> data = {'subject': 'hello', + ... 'message': 'Hi there', + ... 'sender': 'foo@example.com', + ... 'cc_myself': True} + >>> f = ContactForm(data) + +In this dictionary, the keys are the field names, which correspond to the +attributes in your ``Form`` class. The values are the data you're trying +to validate. These will usually be strings, but there's no requirement that +they be strings; the type of data you pass depends on the ``Field``, as we'll +see in a moment. + +If you need to distinguish between bound and unbound form instances at runtime, +check the value of the form's ``is_bound`` attribute:: + + >>> f = ContactForm() + >>> f.is_bound + False + >>> f = ContactForm({'subject': 'hello'}) + >>> f.is_bound + True + +Note that passing an empty dictionary creates a *bound* form with empty data:: + + >>> f = ContactForm({}) + >>> f.is_bound + True + +If you have a bound ``Form`` instance and want to change the data somehow, or +if you want to bind an unbound ``Form`` instance to some data, create another +``Form`` instance. There is no way to change data in a ``Form`` instance. Once +a ``Form`` instance has been created, you should consider its data immutable, +whether it has data or not. + +Using forms to validate data +---------------------------- + +The primary task of a ``Form`` object is to validate data. With a bound +``Form`` instance, call the ``is_valid()`` method to run validation and return +a boolean designating whether the data was valid:: + + >>> data = {'subject': 'hello', + ... 'message': 'Hi there', + ... 'sender': 'foo@example.com', + ... 'cc_myself': True} + >>> f = ContactForm(data) + >>> f.is_valid() + True + +Let's try with some invalid data. In this case, ``subject`` is blank (an error, +because all fields are required by default) and ``sender`` is not a valid +e-mail address:: + + >>> data = {'subject': '', + ... 'message': 'Hi there', + ... 'sender': 'invalid e-mail address', + ... 'cc_myself': True} + >>> f = ContactForm(data) + >>> f.is_valid() + False + +Access the ``Form`` attribute ``errors`` to get a dictionary of error messages:: + + >>> f.errors + {'sender': [u'Enter a valid e-mail address.'], 'subject': [u'This field is required.']} + +In this dictionary, the keys are the field names, and the values are lists of +Unicode strings representing the error messages. The error messages are stored +in lists because a field can have multiple error messages. + +You can access ``errors`` without having to call ``is_valid()`` first. The +form's data will be validated the first time either you call ``is_valid()`` or +access ``errors``. + +Behavior of unbound forms +~~~~~~~~~~~~~~~~~~~~~~~~~ + +It's meaningless to validate a form with no data, but, for the record, here's +what happens with unbound forms:: + + >>> f = ContactForm() + >>> f.is_valid() + False + >>> f.errors + {} + +Accessing "clean" data +---------------------- + +Each ``Field`` in a ``Form`` class is responsible not only for validating data, +but also for "cleaning" it -- normalizing it to a consistent format. This is a +nice feature, because it allows data for a particular field to be input in +a variety of ways, always resulting in consistent output. + +For example, ``DateField`` normalizes input into a Python ``datetime.date`` +object. Regardless of whether you pass it a string in the format +``'1994-07-15'``, a ``datetime.date`` object or a number of other formats, +``DateField`` will always normalize it to a ``datetime.date`` object as long as +it's valid. + +Once you've created a ``Form`` instance with a set of data and validated it, +you can access the clean data via the ``clean_data`` attribute of the ``Form`` +object:: + + >>> data = {'subject': 'hello', + ... 'message': 'Hi there', + ... 'sender': 'foo@example.com', + ... 'cc_myself': True} + >>> f = ContactForm(data) + >>> f.is_valid() + True + >>> f.clean_data + {'cc_myself': True, 'message': u'Hi there', 'sender': u'foo@example.com', 'subject': u'hello'} + +Note that any text-based field -- such as ``CharField`` or ``EmailField`` -- +always cleans the input into a Unicode string. We'll cover the encoding +implications later in this document. + +If your data does *not* validate, your ``Form`` instance will not have a +``clean_data`` attribute:: + + >>> data = {'subject': '', + ... 'message': 'Hi there', + ... 'sender': 'invalid e-mail address', + ... 'cc_myself': True} + >>> f = ContactForm(data) + >>> f.is_valid() + False + >>> f.clean_data + Traceback (most recent call last): + ... + AttributeError: 'ContactForm' object has no attribute 'clean_data' + +``clean_data`` will always *only* contain a key for fields defined in the +``Form``, even if you pass extra data when you define the ``Form``. In this +example, we pass a bunch of extra fields to the ``ContactForm`` constructor, +but ``clean_data`` contains only the form's fields:: + + >>> data = {'subject': 'hello', + ... 'message': 'Hi there', + ... 'sender': 'foo@example.com', + ... 'cc_myself': True, + ... 'extra_field_1': 'foo', + ... 'extra_field_2': 'bar', + ... 'extra_field_3': 'baz'} + >>> f = ContactForm(data) + >>> f.is_valid() + True + >>> f.clean_data # Doesn't contain extra_field_1, etc. + {'cc_myself': True, 'message': u'Hi there', 'sender': u'foo@example.com', 'subject': u'hello'} + +Behavior of unbound forms +~~~~~~~~~~~~~~~~~~~~~~~~~ + +It's meaningless to request "clean" data in a form with no data, but, for the +record, here's what happens with unbound forms:: + + >>> f = ContactForm() + >>> f.clean_data + Traceback (most recent call last): + ... + AttributeError: 'ContactForm' object has no attribute 'clean_data' + +Outputting forms as HTML +------------------------ + +The second task of a ``Form`` object is to render itself as HTML. To do so, +simply ``print`` it:: + + >>> f = ContactForm() + >>> print f + <tr><th><label for="id_subject">Subject:</label></th><td><input id="id_subject" type="text" name="subject" maxlength="100" /></td></tr> + <tr><th><label for="id_message">Message:</label></th><td><input type="text" name="message" id="id_message" /></td></tr> + <tr><th><label for="id_sender">Sender:</label></th><td><input type="text" name="sender" id="id_sender" /></td></tr> + <tr><th><label for="id_cc_myself">Cc myself:</label></th><td><input type="checkbox" name="cc_myself" id="id_cc_myself" /></td></tr> + +If the form is bound to data, the HTML output will include that data +appropriately. For example, if a field is represented by an +``<input type="text">``, the data will be in the ``value`` attribute. If a +field is represented by an ``<input type="checkbox">``, then that HTML will +include ``checked="checked"`` if appropriate:: + + >>> data = {'subject': 'hello', + ... 'message': 'Hi there', + ... 'sender': 'foo@example.com', + ... 'cc_myself': True} + >>> f = ContactForm(data) + >>> print f + <tr><th><label for="id_subject">Subject:</label></th><td><input id="id_subject" type="text" name="subject" maxlength="100" value="hello" /></td></tr> + <tr><th><label for="id_message">Message:</label></th><td><input type="text" name="message" id="id_message" value="Hi there" /></td></tr> + <tr><th><label for="id_sender">Sender:</label></th><td><input type="text" name="sender" id="id_sender" value="foo@example.com" /></td></tr> + <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> + +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><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>' + >>> print f.as_table() + <tr><th><label for="id_subject">Subject:</label></th><td><input id="id_subject" type="text" name="subject" maxlength="100" /></td></tr> + <tr><th><label for="id_message">Message:</label></th><td><input type="text" name="message" id="id_message" /></td></tr> + <tr><th><label for="id_sender">Sender:</label></th><td><input type="text" name="sender" id="id_sender" /></td></tr> + <tr><th><label for="id_cc_myself">Cc myself:</label></th><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><th>Subject:</th><td><input type="text" name="subject" maxlength="100" /></td></tr> + <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 +``initial`` when instantiating the ``Form``, then the latter ``initial`` will +have precedence. In this example, ``initial`` is provided both at the field +level and at the form instance level, and the latter gets precedence:: + + >>> class CommentForm(forms.Form): + ... name = forms.CharField(initial='class') + ... url = forms.URLField() + ... comment = forms.CharField() + >>> f = CommentForm(initial={'name': 'instance'}, auto_id=False) + >>> print f + <tr><th>Name:</th><td><input type="text" name="name" value="instance" /></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> More coming soon ================ @@ -77,3 +825,9 @@ 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 +======= |