基于类的视图

• 基于类的视图
• Using mixins with class-based views

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

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:

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 - - so we can just subclass it,and override the template name:

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 class method instead, which provides a function-like entry to class-basedviews:

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:

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 header indicates when the most recent book was published.Based on this information, the client may or may not download the full objectlist.