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