| """ |
| FormWizard class -- implements a multi-page form, validating between each |
| step and storing the form's state as HTML hidden fields so that no state is |
| stored on the server side. |
| """ |
| |
| import cPickle as pickle |
| |
| from django import forms |
| from django.conf import settings |
| from django.http import Http404 |
| from django.shortcuts import render_to_response |
| from django.template.context import RequestContext |
| from django.utils.hashcompat import md5_constructor |
| |
| class FormWizard(object): |
| # Dictionary of extra template context variables. |
| extra_context = {} |
| |
| # The HTML (and POST data) field name for the "step" variable. |
| step_field_name="wizard_step" |
| |
| # METHODS SUBCLASSES SHOULDN'T OVERRIDE ################################### |
| |
| def __init__(self, form_list, initial=None): |
| "form_list should be a list of Form classes (not instances)." |
| self.form_list = form_list[:] |
| self.initial = initial or {} |
| self.step = 0 # A zero-based counter keeping track of which step we're in. |
| |
| def __repr__(self): |
| return "step: %d\nform_list: %s\ninitial_data: %s" % (self.step, self.form_list, self.initial) |
| |
| def get_form(self, step, data=None): |
| "Helper method that returns the Form instance for the given step." |
| return self.form_list[step](data, prefix=self.prefix_for_step(step), initial=self.initial.get(step, None)) |
| |
| def num_steps(self): |
| "Helper method that returns the number of steps." |
| # You might think we should just set "self.form_list = len(form_list)" |
| # in __init__(), but this calculation needs to be dynamic, because some |
| # hook methods might alter self.form_list. |
| return len(self.form_list) |
| |
| def __call__(self, request, *args, **kwargs): |
| """ |
| Main method that does all the hard work, conforming to the Django view |
| interface. |
| """ |
| if 'extra_context' in kwargs: |
| self.extra_context.update(kwargs['extra_context']) |
| current_step = self.determine_step(request, *args, **kwargs) |
| self.parse_params(request, *args, **kwargs) |
| |
| # Sanity check. |
| if current_step >= self.num_steps(): |
| raise Http404('Step %s does not exist' % current_step) |
| |
| # For each previous step, verify the hash and process. |
| # TODO: Move "hash_%d" to a method to make it configurable. |
| for i in range(current_step): |
| form = self.get_form(i, request.POST) |
| if request.POST.get("hash_%d" % i, '') != self.security_hash(request, form): |
| return self.render_hash_failure(request, i) |
| self.process_step(request, form, i) |
| |
| # Process the current step. If it's valid, go to the next step or call |
| # done(), depending on whether any steps remain. |
| if request.method == 'POST': |
| form = self.get_form(current_step, request.POST) |
| else: |
| form = self.get_form(current_step) |
| if form.is_valid(): |
| self.process_step(request, form, current_step) |
| next_step = current_step + 1 |
| |
| # If this was the last step, validate all of the forms one more |
| # time, as a sanity check, and call done(). |
| num = self.num_steps() |
| if next_step == num: |
| final_form_list = [self.get_form(i, request.POST) for i in range(num)] |
| |
| # Validate all the forms. If any of them fail validation, that |
| # must mean the validator relied on some other input, such as |
| # an external Web site. |
| for i, f in enumerate(final_form_list): |
| if not f.is_valid(): |
| return self.render_revalidation_failure(request, i, f) |
| return self.done(request, final_form_list) |
| |
| # Otherwise, move along to the next step. |
| else: |
| form = self.get_form(next_step) |
| current_step = next_step |
| |
| return self.render(form, request, current_step) |
| |
| def render(self, form, request, step, context=None): |
| "Renders the given Form object, returning an HttpResponse." |
| old_data = request.POST |
| prev_fields = [] |
| if old_data: |
| hidden = forms.HiddenInput() |
| # Collect all data from previous steps and render it as HTML hidden fields. |
| for i in range(step): |
| old_form = self.get_form(i, old_data) |
| hash_name = 'hash_%s' % i |
| prev_fields.extend([bf.as_hidden() for bf in old_form]) |
| prev_fields.append(hidden.render(hash_name, old_data.get(hash_name, self.security_hash(request, old_form)))) |
| return self.render_template(request, form, ''.join(prev_fields), step, context) |
| |
| # METHODS SUBCLASSES MIGHT OVERRIDE IF APPROPRIATE ######################## |
| |
| def prefix_for_step(self, step): |
| "Given the step, returns a Form prefix to use." |
| return str(step) |
| |
| def render_hash_failure(self, request, step): |
| """ |
| Hook for rendering a template if a hash check failed. |
| |
| step is the step that failed. Any previous step is guaranteed to be |
| valid. |
| |
| This default implementation simply renders the form for the given step, |
| but subclasses may want to display an error message, etc. |
| """ |
| 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.'}) |
| |
| def render_revalidation_failure(self, request, step, form): |
| """ |
| Hook for rendering a template if final revalidation failed. |
| |
| It is highly unlikely that this point would ever be reached, but See |
| the comment in __call__() for an explanation. |
| """ |
| return self.render(form, request, step) |
| |
| def security_hash(self, request, form): |
| """ |
| Calculates the security hash for the given HttpRequest and Form instances. |
| |
| This creates a list of the form field names/values in a deterministic |
| order, pickles the result with the SECRET_KEY setting and takes an md5 |
| hash of that. |
| |
| Subclasses may want to take into account request-specific information, |
| such as the IP address. |
| """ |
| data = [(bf.name, bf.data or '') for bf in form] + [settings.SECRET_KEY] |
| # Use HIGHEST_PROTOCOL because it's the most efficient. It requires |
| # Python 2.3, but Django requires 2.3 anyway, so that's OK. |
| pickled = pickle.dumps(data, pickle.HIGHEST_PROTOCOL) |
| return md5_constructor(pickled).hexdigest() |
| |
| def determine_step(self, request, *args, **kwargs): |
| """ |
| Given the request object and whatever *args and **kwargs were passed to |
| __call__(), returns the current step (which is zero-based). |
| |
| Note that the result should not be trusted. It may even be a completely |
| invalid number. It's not the job of this method to validate it. |
| """ |
| if not request.POST: |
| return 0 |
| try: |
| step = int(request.POST.get(self.step_field_name, 0)) |
| except ValueError: |
| return 0 |
| return step |
| |
| def parse_params(self, request, *args, **kwargs): |
| """ |
| Hook for setting some state, given the request object and whatever |
| *args and **kwargs were passed to __call__(), sets some state. |
| |
| This is called at the beginning of __call__(). |
| """ |
| pass |
| |
| def get_template(self, step): |
| """ |
| Hook for specifying the name of the template to use for a given step. |
| |
| Note that this can return a tuple of template names if you'd like to |
| use the template system's select_template() hook. |
| """ |
| return 'forms/wizard.html' |
| |
| def render_template(self, request, form, previous_fields, step, context=None): |
| """ |
| Renders the template for the given step, returning an HttpResponse object. |
| |
| Override this method if you want to add a custom context, return a |
| different MIME type, etc. If you only need to override the template |
| name, use get_template() instead. |
| |
| The template will be rendered with the following context: |
| step_field -- The name of the hidden field containing the step. |
| step0 -- The current step (zero-based). |
| step -- The current step (one-based). |
| step_count -- The total number of steps. |
| form -- The Form instance for the current step (either empty |
| or with errors). |
| previous_fields -- A string representing every previous data field, |
| plus hashes for completed forms, all in the form of |
| hidden fields. Note that you'll need to run this |
| through the "safe" template filter, to prevent |
| auto-escaping, because it's raw HTML. |
| """ |
| context = context or {} |
| context.update(self.extra_context) |
| return render_to_response(self.get_template(self.step), dict(context, |
| step_field=self.step_field_name, |
| step0=step, |
| step=step + 1, |
| step_count=self.num_steps(), |
| form=form, |
| previous_fields=previous_fields |
| ), context_instance=RequestContext(request)) |
| |
| def process_step(self, request, form, step): |
| """ |
| Hook for modifying the FormWizard's internal state, given a fully |
| validated Form object. The Form is guaranteed to have clean, valid |
| data. |
| |
| This method should *not* modify any of that data. Rather, it might want |
| to set self.extra_context or dynamically alter self.form_list, based on |
| previously submitted forms. |
| |
| Note that this method is called every time a page is rendered for *all* |
| submitted steps. |
| """ |
| pass |
| |
| # METHODS SUBCLASSES MUST OVERRIDE ######################################## |
| |
| def done(self, request, form_list): |
| """ |
| Hook for doing something with the validated data. This is responsible |
| for the final processing. |
| |
| form_list is a list of Form instances, each containing clean, valid |
| data. |
| """ |
| raise NotImplementedError("Your %s class has not defined a done() method, which is required." % self.__class__.__name__) |
