视图是可调用的，能接受用户的请求并返回响应。视图远不只是个函数，Django提供了一些可用作视图的类的示例，允许你通过继承和复用构建自己的视图并且复用这些代码。虽然接下来还会介绍一些用于简单任务的通用视图，但你可能想自己设计可复用的视图结构，以便针对某些特殊场景。详情请见 class-based views reference documentation</ref/class-based-views/index> 。
\nDjango provides base view classes which will suit a wide range of applications.\nAll views inherit from the View class, which\nhandles linking the view in to the URLs, HTTP method dispatching and other\nsimple features. RedirectView is for a\nsimple HTTP redirect, and TemplateView\nextends the base class to make it also render a template.
The simplest way to use generic views is to create them directly in your\nURLconf. If you're only changing a few simple attributes on a class-based view,\nyou can simply pass them into the\nas_view() method call itself:
from django.urls import path\nfrom django.views.generic import TemplateView\n\nurlpatterns = [\n path('about/', TemplateView.as_view(template_name="about.html")),\n]\nAny arguments passed to as_view() will\noverride attributes set on the class. In this example, we set template_name\non the TemplateView. A similar overriding pattern can be used for the\nurl attribute on RedirectView.
The second, more powerful way to use generic views is to inherit from an\nexisting view and override attributes (such as the template_name) or\nmethods (such as get_context_data) in your subclass to provide new values\nor methods. Consider, for example, a view that just displays one template,\nabout.html. Django has a generic view to do this -\nTemplateView - so we can just subclass it,\nand override the template name:
# some_app/views.py\nfrom django.views.generic import TemplateView\n\nclass AboutView(TemplateView):\n template_name = "about.html"\nThen we just need to add this new view into our URLconf.\nTemplateView is a class, not a function,\nso we point the URL to the as_view()\nclass method instead, which provides a function-like entry to class-based\nviews:
# urls.py\nfrom django.urls import path\nfrom some_app.views import AboutView\n\nurlpatterns = [\n path('about/', AboutView.as_view()),\n]\nFor more information on how to use the built in generic views, consult the next\ntopic on generic class-based views.
\nSuppose somebody wants to access our book library over HTTP using the views\nas an API. The API client would connect every now and then and download book\ndata for the books published since last visit. But if no new books appeared\nsince then, it is a waste of CPU time and bandwidth to fetch the books from the\ndatabase, render a full response and send it to the client. It might be\npreferable to ask the API when the most recent book was published.
\nWe map the URL to book list view in the URLconf:
\nfrom django.urls import path\nfrom books.views import BookListView\n\nurlpatterns = [\n path('books/', BookListView.as_view()),\n]\nAnd the view:
\nfrom django.http import HttpResponse\nfrom django.views.generic import ListView\nfrom books.models import Book\n\nclass BookListView(ListView):\n model = Book\n\n def head(self, *args, **kwargs):\n last_book = self.get_queryset().latest('publication_date')\n response = HttpResponse('')\n # RFC 1123 date format\n response['Last-Modified'] = last_book.publication_date.strftime('%a, %d %b %Y %H:%M:%S GMT')\n return response\nIf the view is accessed from a GET request, a plain-and-simple object\nlist is returned in the response (using book_list.html template). But if\nthe client issues a HEAD request, the response has an empty body and\nthe Last-Modified header indicates when the most recent book was published.\nBased on this information, the client may or may not download the full object\nlist.