from django.conf.urls import url

from django.contrib import admin

from app01 import views

urlpatterns = [

    url(r'^order/', views.OrderView.as_view()),

]

from django.shortcuts import render

from django.http import JsonResponse

from django.views import View

class OrderView(View):

    def get(self,request,*args,**kwargs):

        ret = {'code': 1000, 'msg': None, 'error': None}

        return JsonResponse(ret)

    # 这是一个类方法

    @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 = OrderView()

            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

            # handler = getattr(self, request.method.lower(), self.http_method_not_allowed)

            # return handler(request, *args, **kwargs)

            # 这个as_view()返回了一个OrderView().dispatch(request, *args, **kwargs)方法

            # 这里返回了dispatch(),所以这个dispath方法会被执行，但是需要从头开始找起

            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=())

        # 由于调用url会views.OrderView.as_view()()所以，这里会执行view函数

        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:

            # 这里利用了反射

            handler = getattr(self, request.method.lower(), self.http_method_not_allowed)

        else:

            handler = self.http_method_not_allowed

        # 最终返回了执行后的handler()

        return handler(request, *args, **kwargs)