django基类View.as_view()

Posted 2020-11-12 _Undo

参考：https://www.zmrenwu.com/post/53/

详细见参考

一般请求的判断方法：

def view(request, *args, **kwargs):
    if request.method.lower() == \'get\':
        do_something()
    if request.method.lower() == \'post\':
        do_something()

 

使用View.as_view()代替判断：

class ClassName(View):
    \'\'\'
    继承View自动判断请求方法
    \'\'\'
    def post():
        pass

    def get():
        pass

    def other():
        pass

#调用方法
url(url, ClassName.as_view(), name)

 

设计思想：把视图函数的逻辑定义到类的方法里面去，然后在函数中实例化这个类，通过调用类的方法实现函数逻辑，而把逻辑定义在类中的一个好处就是可以通过继承复用这些方法。

class View(object):
    """
    Intentionally simple parent class for all views. Only implements
    dispatch-by-method and simple sanity checking.
    """

    http_method_names = [\'get\', \'post\', \'put\', \'patch\', \'delete\', \'head\', \'options\', \'trace\']

    def __init__(self, **kwargs):
        """
        Constructor. Called in the URLconf; can contain helpful extra
        keyword arguments, and other things.
        """
        # Go through keyword arguments, and either save their values to our
        # instance, or raise an error.
        for key, value in six.iteritems(kwargs):
            setattr(self, key, value)

    @classonlymethod
    def as_view(cls, **initkwargs):
        """
        Main entry point for a request-response process.
        """
        for key in initkwargs:
            if key in cls.http_method_names:
                raise TypeError("You tried to pass in the %s method name as a "
                                "keyword argument to %s(). Don\'t do that."
                                % (key, cls.__name__))
            if not hasattr(cls, key):
                raise TypeError("%s() received an invalid keyword %r. as_view "
                                "only accepts arguments that are already "
                                "attributes of the class." % (cls.__name__, key))

        def view(request, *args, **kwargs):
            self = cls(**initkwargs)
            if hasattr(self, \'get\') and not hasattr(self, \'head\'):
                self.head = self.get
            self.request = request
            self.args = args
            self.kwargs = kwargs
            return self.dispatch(request, *args, **kwargs)
        view.view_class = cls
        view.view_initkwargs = initkwargs

        # take name and docstring from class
        update_wrapper(view, cls, updated=())

        # and possible attributes set by decorators
        # like csrf_exempt from dispatch
        update_wrapper(view, cls.dispatch, assigned=())
        return view

    def dispatch(self, request, *args, **kwargs):
        # Try to dispatch to the right method; if a method doesn\'t exist,
        # defer to the error handler. Also defer to the error handler if the
        # request method isn\'t on the approved list.
        if request.method.lower() in self.http_method_names:
            handler = getattr(self, request.method.lower(), self.http_method_not_allowed)
        else:
            handler = self.http_method_not_allowed
        return handler(request, *args, **kwargs)

    def http_method_not_allowed(self, request, *args, **kwargs):
        logger.warning(
            \'Method Not Allowed (%s): %s\', request.method, request.path,
            extra={\'status_code\': 405, \'request\': request}
        )
        return http.HttpResponseNotAllowed(self._allowed_methods())

    def options(self, request, *args, **kwargs):
        """
        Handles responding to requests for the OPTIONS HTTP verb.
        """
        response = http.HttpResponse()
        response[\'Allow\'] = \', \'.join(self._allowed_methods())
        response[\'Content-Length\'] = \'0\'
        return response

    def _allowed_methods(self):
        return [m.upper() for m in self.http_method_names if hasattr(self, m)]

View类源码