Form wizard¶
Django comes with an optional “form wizard” application that splits forms across multiple Web pages. It maintains state in one of the backends so that the full server-side processing can be delayed until the submission of the final form.
You might want to use this if you have a lengthy form that would be too unwieldy for display on a single page. The first page might ask the user for core information, the second page might ask for less important information, etc.
The term “wizard”, in this context, is explained on Wikipedia.
How it works¶
Here’s the basic workflow for how a user would use a wizard:
- The user visits the first page of the wizard, fills in the form and submits it.
- The server validates the data. If it’s invalid, the form is displayed again, with error messages. If it’s valid, the server saves the current state of the wizard in the backend and redirects to the next step.
- Step 1 and 2 repeat, for every subsequent form in the wizard.
- Once the user has submitted all the forms and all the data has been validated, the wizard processes the data – saving it to the database, sending an email, or whatever the application needs to do.
Usage¶
This application handles as much machinery for you as possible. Generally, you just have to do these things:
- Define a number of
Form
classes – one per wizard page. - Create a
WizardView
subclass that specifies what to do once all of your forms have been submitted and validated. This also lets you override some of the wizard’s behavior. - Create some templates that render the forms. You can define a single, generic template to handle every one of the forms, or you can define a specific template for each form.
- Add
django.contrib.formtools
to yourINSTALLED_APPS
list in your settings file. - Point your URLconf at your
WizardView
as_view()
method.
Defining Form
classes¶
The first step in creating a form wizard is to create the
Form
classes. These should be standard
django.forms.Form
classes, covered in the forms documentation. These classes can live anywhere in your codebase,
but convention is to put them in a file called forms.py
in your
application.
For example, let’s write a “contact form” wizard, where the first page’s form
collects the sender’s email address and subject, and the second page collects
the message itself. Here’s what the forms.py
might look like:
from django import forms
class ContactForm1(forms.Form):
subject = forms.CharField(max_length=100)
sender = forms.EmailField()
class ContactForm2(forms.Form):
message = forms.CharField(widget=forms.Textarea)
Note
In order to use FileField
in any form, see the
section Handling files below to learn more about
what to do.
Creating a WizardView
subclass¶
-
class
SessionWizardView
¶
-
class
CookieWizardView
¶
The next step is to create a
django.contrib.formtools.wizard.views.WizardView
subclass. You can
also use the SessionWizardView
or CookieWizardView
classes
which preselect the backend used for storing information during execution of the
wizard (as their names indicate, server-side sessions and browser cookies
respectively).
Note
To use the SessionWizardView
follow the instructions
in the sessions documentation on
how to enable sessions.
We will use the SessionWizardView
in all examples but is is completely
fine to use the CookieWizardView
instead. As with your
Form
classes, this WizardView
class can live
anywhere in your codebase, but convention is to put it in views.py
.
The only requirement on this subclass is that it implement a
done()
method.
-
WizardView.
done
(form_list)¶ This method specifies what should happen when the data for every form is submitted and validated. This method is passed a list of validated
Form
instances.In this simplistic example, rather than performing any database operation, the method simply renders a template of the validated data:
from django.shortcuts import render_to_response from django.contrib.formtools.wizard.views import SessionWizardView class ContactWizard(SessionWizardView): def done(self, form_list, **kwargs): return render_to_response('done.html', { 'form_data': [form.cleaned_data for form in form_list], })
Note that this method will be called via
POST
, so it really ought to be a good Web citizen and redirect after processing the data. Here’s another example:from django.http import HttpResponseRedirect from django.contrib.formtools.wizard.views import SessionWizardView class ContactWizard(SessionWizardView): def done(self, form_list, **kwargs): do_something_with_the_form_data(form_list) return HttpResponseRedirect('/page-to-redirect-to-when-done/')
See the section Advanced WizardView methods
below to learn about more WizardView
hooks.
Creating templates for the forms¶
Next, you’ll need to create a template that renders the wizard’s forms. By
default, every form uses a template called
formtools/wizard/wizard_form.html
. You can change this template name
by overriding either the
template_name
attribute
or the
get_template_names()
method, which are documented in the
TemplateResponseMixin
documentation. The
latter one allows you to use a different template for each form (see the
example below).
This template expects a wizard
object that has various items attached to
it:
form
– TheForm
orBaseFormSet
instance for the current step (either empty or with errors).steps
– A helper object to access the various steps related data:step0
– The current step (zero-based).step1
– The current step (one-based).count
– The total number of steps.first
– The first step.last
– The last step.current
– The current (or first) step.next
– The next step.prev
– The previous step.index
– The index of the current step.all
– A list of all steps of the wizard.
You can supply additional context variables by using the
get_context_data()
method of your WizardView
subclass.
Here’s a full example template:
{% extends "base.html" %}
{% load i18n %}
{% block head %}
{{ wizard.form.media }}
{% endblock %}
{% block content %}
<p>Step {{ wizard.steps.step1 }} of {{ wizard.steps.count }}</p>
<form action="" method="post">{% csrf_token %}
<table>
{{ wizard.management_form }}
{% if wizard.form.forms %}
{{ wizard.form.management_form }}
{% for form in wizard.form.forms %}
{{ form }}
{% endfor %}
{% else %}
{{ wizard.form }}
{% endif %}
</table>
{% if wizard.steps.prev %}
<button name="wizard_goto_step" type="submit" value="{{ wizard.steps.first }}">{% trans "first step" %}</button>
<button name="wizard_goto_step" type="submit" value="{{ wizard.steps.prev }}">{% trans "prev step" %}</button>
{% endif %}
<input type="submit" value="{% trans "submit" %}"/>
</form>
{% endblock %}
Note
Note that {{ wizard.management_form }}
must be used for
the wizard to work properly.
Hooking the wizard into a URLconf¶
-
WizardView.
as_view
()¶
Finally, we need to specify which forms to use in the wizard, and then
deploy the new WizardView
object at a URL in the urls.py
. The
wizard’s as_view()
method takes a list of your
Form
classes as an argument during instantiation:
from django.conf.urls import patterns
from myapp.forms import ContactForm1, ContactForm2
from myapp.views import ContactWizard
urlpatterns = patterns('',
(r'^contact/$', ContactWizard.as_view([ContactForm1, ContactForm2])),
)
Using a different template for each form¶
As mentioned above, you may specify a different template for each form. Consider an example using a form wizard to implement a multi-step checkout process for an online store. In the first step, the user specifies a billing and shipping address. In the second step, the user chooses payment type. If they chose to pay by credit card, they will enter credit card information in the next step. In the final step, they will confirm the purchase.
Here’s what the view code might look like:
from django.http import HttpResponseRedirect
from django.contrib.formtools.wizard.views import SessionWizardView
FORMS = [("address", myapp.forms.AddressForm),
("paytype", myapp.forms.PaymentChoiceForm),
("cc", myapp.forms.CreditCardForm),
("confirmation", myapp.forms.OrderForm)]
TEMPLATES = {"address": "checkout/billingaddress.html",
"paytype": "checkout/paymentmethod.html",
"cc": "checkout/creditcard.html",
"confirmation": "checkout/confirmation.html"}
def pay_by_credit_card(wizard):
"""Return true if user opts to pay by credit card"""
# Get cleaned data from payment step
cleaned_data = wizard.get_cleaned_data_for_step('paytype') or {'method': 'none'}
# Return true if the user selected credit card
return cleaned_data['method'] == 'cc'
class OrderWizard(SessionWizardView):
def get_template_names(self):
return [TEMPLATES[self.steps.current]]
def done(self, form_list, **kwargs):
do_something_with_the_form_data(form_list)
return HttpResponseRedirect('/page-to-redirect-to-when-done/')
...
The urls.py
file would contain something like:
urlpatterns = patterns('',
(r'^checkout/$', OrderWizard.as_view(FORMS, condition_dict={'cc': pay_by_credit_card})),
)
Note that the OrderWizard
object is initialized with a list of pairs.
The first element in the pair is a string that corresponds to the name of the
step and the second is the form class.
In this example, the
get_template_names()
method returns a list containing a single template, which is selected based on
the name of the current step.
Advanced WizardView
methods¶
-
class
WizardView
¶ Aside from the
done()
method,WizardView
offers a few advanced method hooks that let you customize how your wizard works.Some of these methods take an argument
step
, which is a zero-based counter as string representing the current step of the wizard. (E.g., the first form is'0'
and the second form is'1'
)
-
WizardView.
get_form_prefix
(step=None, form=None)¶ Returns the prefix which will be used when calling the form for the given step.
step
contains the step name,form
the form class which will be called with the returned prefix.If no
step
is given, it will be determined automatically. By default, this simply uses the step itself and theform
parameter is not used.For more, see the form prefix documentation.
-
WizardView.
get_form_initial
(step)¶ Returns a dictionary which will be passed as the
initial
argument when instantiating the Form instance for stepstep
. If no initial data was provided while initializing the form wizard, an empty dictionary should be returned.The default implementation:
def get_form_initial(self, step): return self.initial_dict.get(step, {})
-
WizardView.
get_form_kwargs
(step)¶ Returns a dictionary which will be used as the keyword arguments when instantiating the form instance on given
step
.The default implementation:
def get_form_kwargs(self, step): return {}
-
WizardView.
get_form_instance
(step)¶ This method will be called only if a
ModelForm
is used as the form for stepstep
.Returns an
Model
object which will be passed as theinstance
argument when instantiating theModelForm
for stepstep
. If no instance object was provided while initializing the form wizard,None
will be returned.The default implementation:
def get_form_instance(self, step): return self.instance_dict.get(step, None)
-
WizardView.
get_context_data
(form, **kwargs)¶ Returns the template context for a step. You can overwrite this method to add more data for all or some steps. This method returns a dictionary containing the rendered form step.
The default template context variables are:
- Any extra data the storage backend has stored
form
– form instance of the current stepwizard
– the wizard instance itself
Example to add extra variables for a specific step:
def get_context_data(self, form, **kwargs): context = super(MyWizard, self).get_context_data(form=form, **kwargs) if self.steps.current == 'my_step_name': context.update({'another_var': True}) return context
-
WizardView.
get_prefix
(*args, **kwargs)¶ This method returns a prefix for use by the storage backends. Backends use the prefix as a mechanism to allow data to be stored separately for each wizard. This allows wizards to store their data in a single backend without overwriting each other.
You can change this method to make the wizard data prefix more unique to, e.g. have multiple instances of one wizard in one session.
Default implementation:
def get_prefix(self, *args, **kwargs): # use the lowercase underscore version of the class name return normalize_name(self.__class__.__name__)
-
WizardView.
get_form
(step=None, data=None, files=None)¶ This method constructs the form for a given
step
. If nostep
is defined, the current step will be determined automatically. The method gets three arguments:step
– The step for which the form instance should be generated.data
– Gets passed to the form’s data argumentfiles
– Gets passed to the form’s files argument
You can override this method to add extra arguments to the form instance.
Example code to add a user attribute to the form on step 2:
def get_form(self, step=None, data=None, files=None): form = super(MyWizard, self).get_form(step, data, files) if step == '1': form.user = self.request.user return form
-
WizardView.
process_step
(form)¶ Hook for modifying the wizard’s internal state, given a fully validated
Form
object. The Form is guaranteed to have clean, valid data.This method gives you a way to post-process the form data before the data gets stored within the storage backend. By default it just returns the
form.data
dictionary. You should not manipulate the data here but you can use it to do some extra work if needed (e.g. set storage extra data).Note that this method is called every time a page is rendered for all submitted steps.
The default implementation:
def process_step(self, form): return self.get_form_step_data(form)
-
WizardView.
process_step_files
(form)¶ This method gives you a way to post-process the form files before the files gets stored within the storage backend. By default it just returns the
form.files
dictionary. You should not manipulate the data here but you can use it to do some extra work if needed (e.g. set storage extra data).Default implementation:
def process_step_files(self, form): return self.get_form_step_files(form)
-
WizardView.
render_revalidation_failure
(step, form, **kwargs)¶ When the wizard thinks all steps have passed it revalidates all forms with the data from the backend storage.
If any of the forms don’t validate correctly, this method gets called. This method expects two arguments,
step
andform
.The default implementation resets the current step to the first failing form and redirects the user to the invalid form.
Default implementation:
def render_revalidation_failure(self, step, form, **kwargs): self.storage.current_step = step return self.render(form, **kwargs)
-
WizardView.
get_form_step_data
(form)¶ This method fetches the data from the
form
Form instance and returns the dictionary. You can use this method to manipulate the values before the data gets stored in the storage backend.Default implementation:
def get_form_step_data(self, form): return form.data
-
WizardView.
get_form_step_files
(form)¶ This method returns the form files. You can use this method to manipulate the files before the data gets stored in the storage backend.
Default implementation:
def get_form_step_files(self, form): return form.files
-
WizardView.
render
(form, **kwargs)¶ This method gets called after the GET or POST request has been handled. You can hook in this method to, e.g. change the type of HTTP response.
Default implementation:
def render(self, form=None, **kwargs): form = form or self.get_form() context = self.get_context_data(form=form, **kwargs) return self.render_to_response(context)
-
WizardView.
get_cleaned_data_for_step
(step)¶ This method returns the cleaned data for a given
step
. Before returning the cleaned data, the stored values are revalidated through the form. If the data doesn’t validate,None
will be returned.
-
WizardView.
get_all_cleaned_data
()¶ This method returns a merged dictionary of all form steps’
cleaned_data
dictionaries. If a step contains aFormSet
, the key will be prefixed withformset-
and contain a list of the formset’scleaned_data
dictionaries. Note that if two or more steps have a field with the same name, the value for that field from the latest step will overwrite the value from any earlier steps.
Providing initial data for the forms¶
-
WizardView.
initial_dict
¶ Initial data for a wizard’s
Form
objects can be provided using the optionalinitial_dict
keyword argument. This argument should be a dictionary mapping the steps to dictionaries containing the initial data for each step. The dictionary of initial data will be passed along to the constructor of the step’sForm
:>>> from myapp.forms import ContactForm1, ContactForm2 >>> from myapp.views import ContactWizard >>> initial = { ... '0': {'subject': 'Hello', 'sender': 'user@example.com'}, ... '1': {'message': 'Hi there!'} ... } >>> # This example is illustrative only and isn't meant to be run in >>> # the shell since it requires an HttpRequest to pass to the view. >>> wiz = ContactWizard.as_view([ContactForm1, ContactForm2], initial_dict=initial)(request) >>> form1 = wiz.get_form('0') >>> form2 = wiz.get_form('1') >>> form1.initial {'sender': 'user@example.com', 'subject': 'Hello'} >>> form2.initial {'message': 'Hi there!'}
The
initial_dict
can also take a list of dictionaries for a specific step if the step is aFormSet
.
Handling files¶
-
WizardView.
file_storage
¶
To handle FileField
within any step form of the wizard,
you have to add a file_storage
to your WizardView
subclass.
This storage will temporarily store the uploaded files for the wizard. The
file_storage
attribute should be a
Storage
subclass.
Django provides a built-in storage class (see the built-in filesystem storage class):
from django.conf import settings
from django.core.files.storage import FileSystemStorage
class CustomWizardView(WizardView):
...
file_storage = FileSystemStorage(location=os.path.join(settings.MEDIA_ROOT, 'photos'))
Warning
Please remember to take care of removing old files as the
WizardView
won’t remove any files, whether the wizard gets
finished correctly or not.
Conditionally view/skip specific steps¶
-
WizardView.
condition_dict
¶
The as_view()
method accepts a condition_dict
argument.
You can pass a dictionary of boolean values or callables. The key should match
the steps names (e.g. ‘0’, ‘1’).
If the value of a specific step is callable it will be called with the
WizardView
instance as the only argument. If the return value is true,
the step’s form will be used.
This example provides a contact form including a condition. The condition is used to show a message form only if a checkbox in the first step was checked.
The steps are defined in a forms.py
file:
from django import forms
class ContactForm1(forms.Form):
subject = forms.CharField(max_length=100)
sender = forms.EmailField()
leave_message = forms.BooleanField(required=False)
class ContactForm2(forms.Form):
message = forms.CharField(widget=forms.Textarea)
We define our wizard in a views.py
:
from django.shortcuts import render_to_response
from django.contrib.formtools.wizard.views import SessionWizardView
def show_message_form_condition(wizard):
# try to get the cleaned data of step 1
cleaned_data = wizard.get_cleaned_data_for_step('0') or {}
# check if the field ``leave_message`` was checked.
return cleaned_data.get('leave_message', True)
class ContactWizard(SessionWizardView):
def done(self, form_list, **kwargs):
return render_to_response('done.html', {
'form_data': [form.cleaned_data for form in form_list],
})
We need to add the ContactWizard
to our urls.py
file:
from django.conf.urls import patterns
from myapp.forms import ContactForm1, ContactForm2
from myapp.views import ContactWizard, show_message_form_condition
contact_forms = [ContactForm1, ContactForm2]
urlpatterns = patterns('',
(r'^contact/$', ContactWizard.as_view(contact_forms,
condition_dict={'1': show_message_form_condition}
)),
)
As you can see, we defined a show_message_form_condition
next to our
WizardView
subclass and added a condition_dict
argument to the
as_view()
method. The key refers to the second wizard step
(because of the zero based step index).
How to work with ModelForm and ModelFormSet¶
-
WizardView.
instance_dict
¶
WizardView supports ModelForms and
ModelFormSets. Additionally to
initial_dict
, the as_view()
method takes
an instance_dict
argument that should contain model instances for steps
based on ModelForm
and querysets for steps based on ModelFormSet
.
Usage of NamedUrlWizardView
¶
-
class
NamedUrlWizardView
¶
-
class
NamedUrlSessionWizardView
¶
-
class
NamedUrlCookieWizardView
¶
There is a WizardView
subclass which adds named-urls support to the
wizard. By doing this, you can have single urls for every step. You can also
use the NamedUrlSessionWizardView
or NamedUrlCookieWizardView
classes which preselect the backend used for storing information (server-side
sessions and browser cookies respectively).
To use the named urls, you have to change the urls.py
.
Below you will see an example of a contact wizard with two steps, step 1 with “contactdata” as its name and step 2 with “leavemessage” as its name.
Additionally you have to pass two more arguments to the
as_view()
method:
url_name
– the name of the url (as provided in the urls.py)done_step_name
– the name in the url for the done step
Example code for the changed urls.py
file:
from django.conf.urls import url, patterns
from myapp.forms import ContactForm1, ContactForm2
from myapp.views import ContactWizard
named_contact_forms = (
('contactdata', ContactForm1),
('leavemessage', ContactForm2),
)
contact_wizard = ContactWizard.as_view(named_contact_forms,
url_name='contact_step', done_step_name='finished')
urlpatterns = patterns('',
url(r'^contact/(?P<step>.+)/$', contact_wizard, name='contact_step'),
url(r'^contact/$', contact_wizard, name='contact'),
)