三、Mixin扩展类 多继承

1. 多继承

• 首先要清楚： __mro__ 即 继承顺序

1.1 单继承实现:

单继承实现

1.2 多继承实现:

多继承实现

• 程序 从 A 开始调用，虽然貌似B 继承了 object 类，但是super()，会按照 __mro__顺序去查找，而在这里 调用发生在A身上，所以__mro__ 属于A，那么，按顺序 B 会从C找 as_view() 方法，而不是 object 。
  要知道 object 身上 是没有 as_view()方法的，少年!

源码原理(class: view):

@classonlymethod
    def as_view(cls, **initkwargs):
        """
        Main entry point for a request-response process.
        """
        ...省略代码...

        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
            # 调用dispatch方法，按照不同请求方式调用不同请求方法
            return self.dispatch(request, *args, **kwargs)

        ...省略代码...

        # 返回真正的函数视图
        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)