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This patch does not remove all occurrences of the words in question. Rather, I went through all of the occurrences of the words listed below, and judged if they a) suggested the reader had some kind of knowledge/experience, and b) if they added anything of value (including tone of voice, etc). I left most of the words alone. I looked at the following words: - simply/simple - easy/easier/easiest - obvious - just - merely - straightforward - ridiculous Thanks to Carlton Gibson for guidance on how to approach this issue, and to Tim Bell for providing the idea. But the enormous lion's share of thanks go to Adam Johnson for his patient and helpful review.
130 lines
4.7 KiB
Plaintext
130 lines
4.7 KiB
Plaintext
=================
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Class-based views
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=================
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A view is a callable which takes a request and returns a
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response. This can be more than just a function, and Django provides
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an example of some classes which can be used as views. These allow you
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to structure your views and reuse code by harnessing inheritance and
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mixins. There are also some generic views for tasks which we'll get to later,
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but you may want to design your own structure of reusable views which suits
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your use case. For full details, see the :doc:`class-based views reference
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documentation</ref/class-based-views/index>`.
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.. toctree::
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:maxdepth: 1
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intro
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generic-display
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generic-editing
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mixins
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Basic examples
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==============
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Django provides base view classes which will suit a wide range of applications.
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All views inherit from the :class:`~django.views.generic.base.View` class, which
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handles linking the view in to the URLs, HTTP method dispatching and other
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common features. :class:`~django.views.generic.base.RedirectView` provides a
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HTTP redirect, and :class:`~django.views.generic.base.TemplateView` extends the
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base class to make it also render a template.
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Usage in your URLconf
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=====================
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The most direct way to use generic views is to create them directly in your
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URLconf. If you're only changing a few attributes on a class-based view, you
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can pass them into the :meth:`~django.views.generic.base.View.as_view` method
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call itself::
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from django.urls import path
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from django.views.generic import TemplateView
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urlpatterns = [
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path('about/', TemplateView.as_view(template_name="about.html")),
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]
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Any arguments passed to :meth:`~django.views.generic.base.View.as_view` will
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override attributes set on the class. In this example, we set ``template_name``
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on the ``TemplateView``. A similar overriding pattern can be used for the
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``url`` attribute on :class:`~django.views.generic.base.RedirectView`.
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Subclassing generic views
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=========================
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The second, more powerful way to use generic views is to inherit from an
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existing view and override attributes (such as the ``template_name``) or
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methods (such as ``get_context_data``) in your subclass to provide new values
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or methods. Consider, for example, a view that just displays one template,
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``about.html``. Django has a generic view to do this -
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:class:`~django.views.generic.base.TemplateView` - so we can subclass it, and
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override the template name::
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# some_app/views.py
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from django.views.generic import TemplateView
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class AboutView(TemplateView):
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template_name = "about.html"
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Then we need to add this new view into our URLconf.
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:class:`~django.views.generic.base.TemplateView` is a class, not a function, so
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we point the URL to the :meth:`~django.views.generic.base.View.as_view` class
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method instead, which provides a function-like entry to class-based views::
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# urls.py
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from django.urls import path
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from some_app.views import AboutView
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urlpatterns = [
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path('about/', AboutView.as_view()),
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]
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For more information on how to use the built in generic views, consult the next
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topic on :doc:`generic class-based views</topics/class-based-views/generic-display>`.
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.. _supporting-other-http-methods:
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Supporting other HTTP methods
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-----------------------------
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Suppose somebody wants to access our book library over HTTP using the views
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as an API. The API client would connect every now and then and download book
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data for the books published since last visit. But if no new books appeared
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since then, it is a waste of CPU time and bandwidth to fetch the books from the
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database, render a full response and send it to the client. It might be
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preferable to ask the API when the most recent book was published.
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We map the URL to book list view in the URLconf::
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from django.urls import path
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from books.views import BookListView
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urlpatterns = [
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path('books/', BookListView.as_view()),
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]
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And the view::
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from django.http import HttpResponse
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from django.views.generic import ListView
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from books.models import Book
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class BookListView(ListView):
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model = Book
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def head(self, *args, **kwargs):
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last_book = self.get_queryset().latest('publication_date')
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response = HttpResponse()
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# RFC 1123 date format
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response['Last-Modified'] = last_book.publication_date.strftime('%a, %d %b %Y %H:%M:%S GMT')
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return response
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If the view is accessed from a ``GET`` request, an object list is returned in
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the response (using the ``book_list.html`` template). But if the client issues
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a ``HEAD`` request, the response has an empty body and the ``Last-Modified``
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header indicates when the most recent book was published. Based on this
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information, the client may or may not download the full object list.
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