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241 lines
9.9 KiB
241 lines
9.9 KiB
""" |
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FormWizard class -- implements a multi-page form, validating between each |
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step and storing the form's state as HTML hidden fields so that no state is |
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stored on the server side. |
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""" |
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import cPickle as pickle |
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from django import forms |
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from django.conf import settings |
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from django.http import Http404 |
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from django.shortcuts import render_to_response |
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from django.template.context import RequestContext |
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from django.utils.hashcompat import md5_constructor |
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from django.utils.translation import ugettext_lazy as _ |
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from django.contrib.formtools.utils import security_hash |
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class FormWizard(object): |
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# Dictionary of extra template context variables. |
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extra_context = {} |
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# The HTML (and POST data) field name for the "step" variable. |
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step_field_name="wizard_step" |
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# METHODS SUBCLASSES SHOULDN'T OVERRIDE ################################### |
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def __init__(self, form_list, initial=None): |
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"form_list should be a list of Form classes (not instances)." |
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self.form_list = form_list[:] |
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self.initial = initial or {} |
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self.step = 0 # A zero-based counter keeping track of which step we're in. |
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def __repr__(self): |
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return "step: %d\nform_list: %s\ninitial_data: %s" % (self.step, self.form_list, self.initial) |
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def get_form(self, step, data=None): |
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"Helper method that returns the Form instance for the given step." |
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return self.form_list[step](data, prefix=self.prefix_for_step(step), initial=self.initial.get(step, None)) |
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def num_steps(self): |
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"Helper method that returns the number of steps." |
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# You might think we should just set "self.form_list = len(form_list)" |
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# in __init__(), but this calculation needs to be dynamic, because some |
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# hook methods might alter self.form_list. |
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return len(self.form_list) |
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def __call__(self, request, *args, **kwargs): |
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""" |
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Main method that does all the hard work, conforming to the Django view |
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interface. |
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""" |
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if 'extra_context' in kwargs: |
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self.extra_context.update(kwargs['extra_context']) |
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current_step = self.determine_step(request, *args, **kwargs) |
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self.parse_params(request, *args, **kwargs) |
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# Sanity check. |
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if current_step >= self.num_steps(): |
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raise Http404('Step %s does not exist' % current_step) |
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# For each previous step, verify the hash and process. |
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# TODO: Move "hash_%d" to a method to make it configurable. |
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for i in range(current_step): |
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form = self.get_form(i, request.POST) |
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if request.POST.get("hash_%d" % i, '') != self.security_hash(request, form): |
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return self.render_hash_failure(request, i) |
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self.process_step(request, form, i) |
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# Process the current step. If it's valid, go to the next step or call |
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# done(), depending on whether any steps remain. |
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if request.method == 'POST': |
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form = self.get_form(current_step, request.POST) |
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else: |
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form = self.get_form(current_step) |
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if form.is_valid(): |
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self.process_step(request, form, current_step) |
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next_step = current_step + 1 |
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# If this was the last step, validate all of the forms one more |
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# time, as a sanity check, and call done(). |
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num = self.num_steps() |
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if next_step == num: |
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final_form_list = [self.get_form(i, request.POST) for i in range(num)] |
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# Validate all the forms. If any of them fail validation, that |
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# must mean the validator relied on some other input, such as |
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# an external Web site. |
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for i, f in enumerate(final_form_list): |
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if not f.is_valid(): |
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return self.render_revalidation_failure(request, i, f) |
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return self.done(request, final_form_list) |
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# Otherwise, move along to the next step. |
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else: |
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form = self.get_form(next_step) |
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self.step = current_step = next_step |
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return self.render(form, request, current_step) |
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def render(self, form, request, step, context=None): |
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"Renders the given Form object, returning an HttpResponse." |
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old_data = request.POST |
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prev_fields = [] |
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if old_data: |
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hidden = forms.HiddenInput() |
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# Collect all data from previous steps and render it as HTML hidden fields. |
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for i in range(step): |
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old_form = self.get_form(i, old_data) |
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hash_name = 'hash_%s' % i |
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prev_fields.extend([bf.as_hidden() for bf in old_form]) |
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prev_fields.append(hidden.render(hash_name, old_data.get(hash_name, self.security_hash(request, old_form)))) |
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return self.render_template(request, form, ''.join(prev_fields), step, context) |
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# METHODS SUBCLASSES MIGHT OVERRIDE IF APPROPRIATE ######################## |
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def prefix_for_step(self, step): |
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"Given the step, returns a Form prefix to use." |
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return str(step) |
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def render_hash_failure(self, request, step): |
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""" |
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Hook for rendering a template if a hash check failed. |
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step is the step that failed. Any previous step is guaranteed to be |
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valid. |
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This default implementation simply renders the form for the given step, |
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but subclasses may want to display an error message, etc. |
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""" |
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return self.render(self.get_form(step), request, step, context={'wizard_error': _('We apologize, but your form has expired. Please continue filling out the form from this page.')}) |
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def render_revalidation_failure(self, request, step, form): |
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""" |
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Hook for rendering a template if final revalidation failed. |
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It is highly unlikely that this point would ever be reached, but See |
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the comment in __call__() for an explanation. |
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""" |
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return self.render(form, request, step) |
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def security_hash(self, request, form): |
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""" |
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Calculates the security hash for the given HttpRequest and Form instances. |
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Subclasses may want to take into account request-specific information, |
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such as the IP address. |
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""" |
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return security_hash(request, form) |
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def determine_step(self, request, *args, **kwargs): |
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""" |
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Given the request object and whatever *args and **kwargs were passed to |
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__call__(), returns the current step (which is zero-based). |
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Note that the result should not be trusted. It may even be a completely |
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invalid number. It's not the job of this method to validate it. |
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""" |
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if not request.POST: |
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return 0 |
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try: |
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step = int(request.POST.get(self.step_field_name, 0)) |
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except ValueError: |
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return 0 |
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return step |
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def parse_params(self, request, *args, **kwargs): |
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""" |
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Hook for setting some state, given the request object and whatever |
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*args and **kwargs were passed to __call__(), sets some state. |
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This is called at the beginning of __call__(). |
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""" |
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pass |
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def get_template(self, step): |
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""" |
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Hook for specifying the name of the template to use for a given step. |
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Note that this can return a tuple of template names if you'd like to |
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use the template system's select_template() hook. |
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""" |
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return 'forms/wizard.html' |
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def render_template(self, request, form, previous_fields, step, context=None): |
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""" |
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Renders the template for the given step, returning an HttpResponse object. |
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Override this method if you want to add a custom context, return a |
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different MIME type, etc. If you only need to override the template |
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name, use get_template() instead. |
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The template will be rendered with the following context: |
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step_field -- The name of the hidden field containing the step. |
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step0 -- The current step (zero-based). |
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step -- The current step (one-based). |
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step_count -- The total number of steps. |
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form -- The Form instance for the current step (either empty |
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or with errors). |
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previous_fields -- A string representing every previous data field, |
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plus hashes for completed forms, all in the form of |
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hidden fields. Note that you'll need to run this |
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through the "safe" template filter, to prevent |
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auto-escaping, because it's raw HTML. |
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""" |
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context = context or {} |
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context.update(self.extra_context) |
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return render_to_response(self.get_template(step), dict(context, |
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step_field=self.step_field_name, |
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step0=step, |
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step=step + 1, |
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step_count=self.num_steps(), |
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form=form, |
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previous_fields=previous_fields |
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), context_instance=RequestContext(request)) |
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def process_step(self, request, form, step): |
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""" |
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Hook for modifying the FormWizard's internal state, given a fully |
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validated Form object. The Form is guaranteed to have clean, valid |
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data. |
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This method should *not* modify any of that data. Rather, it might want |
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to set self.extra_context or dynamically alter self.form_list, based on |
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previously submitted forms. |
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Note that this method is called every time a page is rendered for *all* |
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submitted steps. |
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""" |
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pass |
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# METHODS SUBCLASSES MUST OVERRIDE ######################################## |
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def done(self, request, form_list): |
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""" |
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Hook for doing something with the validated data. This is responsible |
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for the final processing. |
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form_list is a list of Form instances, each containing clean, valid |
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data. |
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""" |
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raise NotImplementedError("Your %s class has not defined a done() method, which is required." % self.__class__.__name__)
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