基于类的视图

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> 。

• 基于类的视图
• Built-in class-based generic views
• Form handling with class-based views
• Using mixins with class-based views

Basic examples

Django provides base view classes which will suit a wide range of applications.All views inherit from the View class, whichhandles linking the view in to the URLs, HTTP method dispatching and othersimple features. RedirectView is for asimple HTTP redirect, and TemplateViewextends the base class to make it also render a template.

Simple usage in your URLconf

The simplest way to use generic views is to create them directly in yourURLconf. If you're only changing a few simple attributes on a class-based view,you can simply pass them into theas_view() method call itself:

from django.urls import path
from django.views.generic import TemplateView
 
urlpatterns = [
    path('about/', TemplateView.as_view(template_name="about.html")),
]

Any arguments passed to as_view() willoverride attributes set on the class. In this example, we set template_nameon the TemplateView. A similar overriding pattern can be used for theurl attribute on RedirectView.

Subclassing generic views

The second, more powerful way to use generic views is to inherit from anexisting view and override attributes (such as the template_name) ormethods (such as get_context_data) in your subclass to provide new valuesor methods. Consider, for example, a view that just displays one template,about.html. Django has a generic view to do this -TemplateView - so we can just subclass it,and override the template name:

# some_app/views.py
from django.views.generic import TemplateView
 
class AboutView(TemplateView):
    template_name = "about.html"

Then we just need to add this new view into our URLconf.TemplateView is a class, not a function,so we point the URL to the as_view()class method instead, which provides a function-like entry to class-basedviews:

# urls.py
from django.urls import path
from some_app.views import AboutView
 
urlpatterns = [
    path('about/', AboutView.as_view()),
]

For more information on how to use the built in generic views, consult the nexttopic on generic class-based views.

Supporting other HTTP methods

Suppose somebody wants to access our book library over HTTP using the viewsas an API. The API client would connect every now and then and download bookdata for the books published since last visit. But if no new books appearedsince then, it is a waste of CPU time and bandwidth to fetch the books from thedatabase, render a full response and send it to the client. It might bepreferable to ask the API when the most recent book was published.

We map the URL to book list view in the URLconf:

from django.urls import path
from books.views import BookListView
 
urlpatterns = [
    path('books/', BookListView.as_view()),
]

And the view:

from django.http import HttpResponse
from django.views.generic import ListView
from books.models import Book
 
class BookListView(ListView):
    model = Book
 
    def head(self, *args, **kwargs):
        last_book = self.get_queryset().latest('publication_date')
        response = HttpResponse('')
        # RFC 1123 date format
        response['Last-Modified'] = last_book.publication_date.strftime('%a, %d %b %Y %H:%M:%S GMT')
        return response

If the view is accessed from a GET request, a plain-and-simple objectlist is returned in the response (using book_list.html template). But ifthe client issues a HEAD request, the response has an empty body andthe Last-Modified header indicates when the most recent book was published.Based on this information, the client may or may not download the full objectlist.