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Thanks Aymeric Augustin for shepherding the DEP and patch review. Thanks Marten Kenbeek and Tim Graham for contributing to the code. Thanks Tom Christie, Shai Berger, and Tim Graham for the docs.
264 lines
8.8 KiB
Plaintext
264 lines
8.8 KiB
Plaintext
====================================
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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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.. snippet::
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:filename: 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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.. snippet::
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:filename: 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().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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.. snippet::
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:filename: models.py
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from django.urls 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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.. snippet::
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:filename: views.py
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from django.views.generic.edit import CreateView, UpdateView, DeleteView
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from django.urls 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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fields = ['name']
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class AuthorUpdate(UpdateView):
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model = Author
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fields = ['name']
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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.urls.reverse_lazy` here, not just
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``reverse()`` as the urls are not loaded when the file is imported.
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The ``fields`` attribute works the same way as the ``fields`` attribute on the
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inner ``Meta`` class on :class:`~django.forms.ModelForm`. Unless you define the
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form class in another way, the attribute is required and the view will raise
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an :exc:`~django.core.exceptions.ImproperlyConfigured` exception if it's not.
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If you specify both the :attr:`~django.views.generic.edit.ModelFormMixin.fields`
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and :attr:`~django.views.generic.edit.FormMixin.form_class` attributes, an
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:exc:`~django.core.exceptions.ImproperlyConfigured` exception will be raised.
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Finally, we hook these new views into the URLconf:
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.. snippet::
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:filename: urls.py
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from django.urls import path
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from myapp.views import AuthorCreate, AuthorUpdate, AuthorDelete
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urlpatterns = [
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# ...
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path('author/add/', AuthorCreate.as_view(), name='author-add'),
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path('author/<int:pk>/', AuthorUpdate.as_view(), name='author-update'),
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path('author/<int:pk>/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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.. snippet::
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:filename: models.py
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from django.contrib.auth.models 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, on_delete=models.CASCADE)
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# ...
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In the view, ensure that you don't include ``created_by`` in the list of fields
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to edit, and override
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:meth:`~django.views.generic.edit.ModelFormMixin.form_valid()` to add the user:
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.. snippet::
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:filename: 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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class AuthorCreate(CreateView):
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model = Author
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fields = ['name']
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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().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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from django.http import JsonResponse
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from django.views.generic.edit import CreateView
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from myapp.models import Author
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class AjaxableResponseMixin:
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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 form_invalid(self, form):
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response = super().form_invalid(form)
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if self.request.is_ajax():
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return JsonResponse(form.errors, status=400)
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else:
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return response
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def form_valid(self, form):
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# We make sure to call the parent's form_valid() method because
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# it might do some processing (in the case of CreateView, it will
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# call form.save() for example).
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response = super().form_valid(form)
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if self.request.is_ajax():
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data = {
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'pk': self.object.pk,
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}
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return JsonResponse(data)
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else:
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return response
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class AuthorCreate(AjaxableResponseMixin, CreateView):
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model = Author
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fields = ['name']
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