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257 lines
8.6 KiB
Plaintext
257 lines
8.6 KiB
Plaintext
Form handling with class-based views
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====================================
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Form processing generally has 3 paths:
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* Initial GET (blank or prepopulated form)
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* POST with invalid data (typically redisplay form with errors)
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* POST with valid data (process the data and typically redirect)
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Implementing this yourself often results in a lot of repeated boilerplate code
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(see :ref:`Using a form in a view<using-a-form-in-a-view>`). To help avoid
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this, Django provides a collection of generic class-based views for form
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processing.
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Basic Forms
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-----------
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Given a simple contact form::
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# forms.py
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from django import forms
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class ContactForm(forms.Form):
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name = forms.CharField()
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message = forms.CharField(widget=forms.Textarea)
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def send_email(self):
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# send email using the self.cleaned_data dictionary
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pass
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The view can be constructed using a ``FormView``::
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# views.py
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from myapp.forms import ContactForm
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from django.views.generic.edit import FormView
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class ContactView(FormView):
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template_name = 'contact.html'
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form_class = ContactForm
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success_url = '/thanks/'
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def form_valid(self, form):
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# This method is called when valid form data has been POSTed.
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# It should return an HttpResponse.
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form.send_email()
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return super(ContactView, self).form_valid(form)
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Notes:
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* FormView inherits
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:class:`~django.views.generic.base.TemplateResponseMixin` so
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:attr:`~django.views.generic.base.TemplateResponseMixin.template_name`
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can be used here.
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* The default implementation for
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:meth:`~django.views.generic.edit.FormMixin.form_valid` simply
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redirects to the :attr:`~django.views.generic.edit.FormMixin.success_url`.
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Model Forms
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-----------
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Generic views really shine when working with models. These generic
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views will automatically create a :class:`~django.forms.ModelForm`, so long as
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they can work out which model class to use:
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* If the :attr:`~django.views.generic.edit.ModelFormMixin.model` attribute is
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given, that model class will be used.
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* If :meth:`~django.views.generic.detail.SingleObjectMixin.get_object()`
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returns an object, the class of that object will be used.
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* If a :attr:`~django.views.generic.detail.SingleObjectMixin.queryset` is
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given, the model for that queryset will be used.
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Model form views provide a
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:meth:`~django.views.generic.edit.ModelFormMixin.form_valid()` implementation
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that saves the model automatically. You can override this if you have any
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special requirements; see below for examples.
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You don't even need to provide a ``success_url`` for
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:class:`~django.views.generic.edit.CreateView` or
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:class:`~django.views.generic.edit.UpdateView` - they will use
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:meth:`~django.db.models.Model.get_absolute_url()` on the model object if available.
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If you want to use a custom :class:`~django.forms.ModelForm` (for instance to
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add extra validation) simply set
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:attr:`~django.views.generic.edit.FormMixin.form_class` on your view.
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.. note::
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When specifying a custom form class, you must still specify the model,
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even though the :attr:`~django.views.generic.edit.FormMixin.form_class` may
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be a :class:`~django.forms.ModelForm`.
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First we need to add :meth:`~django.db.models.Model.get_absolute_url()` to our
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``Author`` class:
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.. code-block:: python
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# models.py
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from django.core.urlresolvers import reverse
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from django.db import models
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class Author(models.Model):
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name = models.CharField(max_length=200)
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def get_absolute_url(self):
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return reverse('author-detail', kwargs={'pk': self.pk})
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Then we can use :class:`CreateView` and friends to do the actual
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work. Notice how we're just configuring the generic class-based views
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here; we don't have to write any logic ourselves::
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# views.py
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from django.views.generic.edit import CreateView, UpdateView, DeleteView
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from django.core.urlresolvers import reverse_lazy
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from myapp.models import Author
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class AuthorCreate(CreateView):
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model = Author
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class AuthorUpdate(UpdateView):
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model = Author
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class AuthorDelete(DeleteView):
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model = Author
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success_url = reverse_lazy('author-list')
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.. note::
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We have to use :func:`~django.core.urlresolvers.reverse_lazy` here, not
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just ``reverse`` as the urls are not loaded when the file is imported.
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Finally, we hook these new views into the URLconf::
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# urls.py
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from django.conf.urls import patterns, url
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from myapp.views import AuthorCreate, AuthorUpdate, AuthorDelete
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urlpatterns = patterns('',
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# ...
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url(r'author/add/$', AuthorCreate.as_view(), name='author_add'),
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url(r'author/(?P<pk>\d+)/$', AuthorUpdate.as_view(), name='author_update'),
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url(r'author/(?P<pk>\d+)/delete/$', AuthorDelete.as_view(), name='author_delete'),
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)
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.. note::
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These views inherit
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:class:`~django.views.generic.detail.SingleObjectTemplateResponseMixin`
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which uses
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:attr:`~django.views.generic.detail.SingleObjectTemplateResponseMixin.template_name_suffix`
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to construct the
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:attr:`~django.views.generic.base.TemplateResponseMixin.template_name`
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based on the model.
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In this example:
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* :class:`CreateView` and :class:`UpdateView` use ``myapp/author_form.html``
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* :class:`DeleteView` uses ``myapp/author_confirm_delete.html``
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If you wish to have separate templates for :class:`CreateView` and
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:class:`UpdateView`, you can set either
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:attr:`~django.views.generic.base.TemplateResponseMixin.template_name` or
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:attr:`~django.views.generic.detail.SingleObjectTemplateResponseMixin.template_name_suffix`
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on your view class.
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Models and request.user
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-----------------------
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To track the user that created an object using a :class:`CreateView`,
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you can use a custom :class:`~django.forms.ModelForm` to do this. First, add
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the foreign key relation to the model::
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# models.py
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from django.contrib.auth import User
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from django.db import models
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class Author(models.Model):
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name = models.CharField(max_length=200)
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created_by = models.ForeignKey(User)
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# ...
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Create a custom :class:`~django.forms.ModelForm` in order to exclude the
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``created_by`` field and prevent the user from editing it:
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.. code-block:: python
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# forms.py
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from django import forms
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from myapp.models import Author
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class AuthorForm(forms.ModelForm):
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class Meta:
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model = Author
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exclude = ('created_by',)
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In the view, use the custom
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:attr:`~django.views.generic.edit.FormMixin.form_class` and override
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:meth:`~django.views.generic.edit.ModelFormMixin.form_valid()` to add the
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user::
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# views.py
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from django.views.generic.edit import CreateView
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from myapp.models import Author
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from myapp.forms import AuthorForm
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class AuthorCreate(CreateView):
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form_class = AuthorForm
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model = Author
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def form_valid(self, form):
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form.instance.created_by = self.request.user
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return super(AuthorCreate, self).form_valid(form)
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Note that you'll need to :ref:`decorate this
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view<decorating-class-based-views>` using
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:func:`~django.contrib.auth.decorators.login_required`, or
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alternatively handle unauthorized users in the
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:meth:`~django.views.generic.edit.ModelFormMixin.form_valid()`.
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AJAX example
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------------
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Here is a simple example showing how you might go about implementing a form that
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works for AJAX requests as well as 'normal' form POSTs::
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import json
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from django.http import HttpResponse
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from django.views.generic.edit import CreateView
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from django.views.generic.detail import SingleObjectTemplateResponseMixin
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class AjaxableResponseMixin(object):
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"""
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Mixin to add AJAX support to a form.
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Must be used with an object-based FormView (e.g. CreateView)
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"""
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def render_to_json_response(self, context, **response_kwargs):
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data = json.dumps(context)
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response_kwargs['content_type'] = 'application/json'
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return HttpResponse(data, **response_kwargs)
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def form_invalid(self, form):
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if self.request.is_ajax():
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return self.render_to_json_response(form.errors, status=400)
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else:
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return super(AjaxableResponseMixin, self).form_invalid(form)
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def form_valid(self, form):
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if self.request.is_ajax():
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data = {
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'pk': form.instance.pk,
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}
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return self.render_to_json_response(data)
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else:
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return super(AjaxableResponseMixin, self).form_valid(form)
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class AuthorCreate(AjaxableResponseMixin, CreateView):
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model = Author
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