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62 lines
2.2 KiB
Text
62 lines
2.2 KiB
Text
=================
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Class-based views
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=================
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Class-based views API reference. For introductory material, see
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:doc:`/topics/class-based-views/index`.
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.. toctree::
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:maxdepth: 3
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base
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generic-display
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generic-editing
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generic-date-based
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mixins
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flattened-index
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Specification
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-------------
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Each request served by a class-based view has an independent state; therefore,
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it is safe to store state variables on the instance (i.e., ``self.foo = 3`` is
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a thread-safe operation).
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A class-based view is deployed into a URL pattern using the
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:meth:`~django.views.generic.base.View.as_view()` classmethod::
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urlpatterns = [
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url(r'^view/$', MyView.as_view(size=42)),
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]
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.. admonition:: Thread safety with view arguments
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Arguments passed to a view are shared between every instance of a view.
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This means that you shouldn't use a list, dictionary, or any other
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mutable object as an argument to a view. If you do and the shared object
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is modified, the actions of one user visiting your view could have an
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effect on subsequent users visiting the same view.
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Arguments passed into :meth:`~django.views.generic.base.View.as_view()` will
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be assigned onto the instance that is used to service a request. Using the
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previous example, this means that every request on ``MyView`` is able to use
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``self.size``. Arguments must correspond to attributes that already exist on
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the class (return ``True`` on a ``hasattr`` check).
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Base vs Generic views
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---------------------
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Base class-based views can be thought of as *parent* views, which can be
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used by themselves or inherited from. They may not provide all the
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capabilities required for projects, in which case there are Mixins which
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extend what base views can do.
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Django’s generic views are built off of those base views, and were developed
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as a shortcut for common usage patterns such as displaying the details of an
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object. They take certain common idioms and patterns found in view
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development and abstract them so that you can quickly write common views of
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data without having to repeat yourself.
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Most generic views require the ``queryset`` key, which is a ``QuerySet``
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instance; see :doc:`/topics/db/queries` for more information about ``QuerySet``
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objects.
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