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+============
+Form preview
+============
+
+.. module:: django.contrib.formtools
+ :synopsis: Displays an HTML form, forces a preview, then does something
+ with the submission.
+
+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 :class:`django.forms.Form` subclass that you define, this
+application takes care of the following workflow:
+
+ 1. Displays the form as HTML on a Web page.
+ 2. 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.
+ 3. When the "confirmation" form is submitted from the preview page, calls
+ a hook that you define -- a
+ :meth:`~django.contrib.formtools.FormPreview.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``
+==========================
+
+ 1. Point Django at the default FormPreview templates. There are two ways to
+ do this:
+
+ * Add ``'django.contrib.formtools'`` to your
+ :setting:`INSTALLED_APPS` setting. This will work if your
+ :setting:`TEMPLATE_LOADERS` setting includes the
+ ``app_directories`` template loader (which is the case by
+ default). See the :ref:`template loader docs <template-loaders>`
+ for more.
+
+ * Otherwise, determine the full filesystem path to the
+ :file:`django/contrib/formtools/templates` directory, and add that
+ directory to your :setting:`TEMPLATE_DIRS` setting.
+
+ 2. Create a :class:`~django.contrib.formtools.FormPreview` subclass that
+ overrides the :meth:`~django.contrib.formtools.FormPreview.done()`
+ 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 :class:`~django.http.HttpRequest` object and a
+ dictionary of the form data after it has been validated and cleaned.
+ It should return an :class:`~django.http.HttpResponseRedirect` that
+ is the end result of the form being submitted.
+
+ 3. Change your URLconf to point to an instance of your
+ :class:`~django.contrib.formtools.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.
+
+ 4. Run the Django server and visit :file:`/post/` in your browser.
+
+``FormPreview`` classes
+=======================
+
+.. class:: FormPreview
+
+A :class:`~django.contrib.formtools.FormPreview` class is a simple Python class
+that represents the preview workflow.
+:class:`~django.contrib.formtools.FormPreview` classes must subclass
+``django.contrib.formtools.preview.FormPreview`` and override the
+:meth:`~django.contrib.formtools.FormPreview.done()` method. They can live
+anywhere in your codebase.
+
+``FormPreview`` templates
+=========================
+
+By default, the form is rendered via the template :file:`formtools/form.html`,
+and the preview page is rendered via the template :file:`formtools/preview.html`.
+These values can be overridden for a particular form preview by setting
+:attr:`~django.contrib.formtools.FormPreview.preview_template` and
+:attr:`~django.contrib.formtools.FormPreview.form_template` attributes on the
+FormPreview subclass. See :file:`django/contrib/formtools/templates` for the
+default templates.
+
+Advanced ``FormPreview`` methods
+================================
+
+.. versionadded:: 1.2
+
+.. method:: 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.