Form preview¶
Django comes with an optional “form preview” application that helps automate the following workflow:
“Display an HTML form, force a preview, then do something with the submission.”
To force a preview of a form submission, all you have to do is write a short Python class.
Overview¶
Given a django.forms.Form
subclass that you define, this
application takes care of the following workflow:
- Displays the form as HTML on a Web page.
- Validates the form data when it’s submitted via POST. a. If it’s valid, displays a preview page. b. If it’s not valid, redisplays the form with error messages.
- When the “confirmation” form is submitted from the preview page, calls
a hook that you define – a
done()
method that gets passed the valid data.
The framework enforces the required preview by passing a shared-secret hash to the preview page via hidden form fields. If somebody tweaks the form parameters on the preview page, the form submission will fail the hash-comparison test.
How to use FormPreview
¶
Point Django at the default FormPreview templates. There are two ways to do this:
- Add
'django.contrib.formtools'
to yourINSTALLED_APPS
setting. This will work if yourTEMPLATE_LOADERS
setting includes theapp_directories
template loader (which is the case by default). See the template loader docs for more. - Otherwise, determine the full filesystem path to the
django/contrib/formtools/templates
directory, and add that directory to yourTEMPLATE_DIRS
setting.
- Add
Create a
FormPreview
subclass that overrides thedone()
method:from django.contrib.formtools.preview import FormPreview from myapp.models import SomeModel class SomeModelFormPreview(FormPreview): def done(self, request, cleaned_data): # Do something with the cleaned_data, then redirect # to a "success" page. return HttpResponseRedirect('/form/success')
This method takes an
HttpRequest
object and a dictionary of the form data after it has been validated and cleaned. It should return anHttpResponseRedirect
that is the end result of the form being submitted.Change your URLconf to point to an instance of your
FormPreview
subclass:from myapp.preview import SomeModelFormPreview from myapp.forms import SomeModelForm from django import forms
...and add the following line to the appropriate model in your URLconf:
(r'^post/$', SomeModelFormPreview(SomeModelForm)),
where
SomeModelForm
is a Form or ModelForm class for the model.Run the Django server and visit
/post/
in your browser.
FormPreview
classes¶
-
class
FormPreview
¶
A FormPreview
class is a simple Python class
that represents the preview workflow.
FormPreview
classes must subclass
django.contrib.formtools.preview.FormPreview
and override the done()
method. They can live anywhere in your codebase.
FormPreview
templates¶
-
FormPreview.
form_template
¶
-
FormPreview.
preview_template
¶
By default, the form is rendered via the template formtools/form.html
,
and the preview page is rendered via the template formtools/preview.html
.
These values can be overridden for a particular form preview by setting
preview_template
and
form_template
attributes on the
FormPreview subclass. See django/contrib/formtools/templates
for the
default templates.
Advanced FormPreview
methods¶
-
FormPreview.
process_preview
()¶ Given a validated form, performs any extra processing before displaying the preview page, and saves any extra data in context.
By default, this method is empty. It is called after the form is validated, but before the context is modified with hash information and rendered.