CBV请求流程源码分析

一、CBV流程解析

urls.py

urlpatterns = [

    url(r'^admin/', admin.site.urls),

    url(r'^book/', views.BookView.as_view()),

]

views.py

from django.views import View

class BookView(View):

    def get(self,request):

        return HttpResponse("get.........")

    def post(self,request):

        return HttpResponse("post........")

请求走到url中，怎么执行的？

1、先找BookView中as_view方法，没有找到，找父类View，找到View中的as_view执行，返回view

2、执行View中的view，返回结果self.dispatch，self为自定义的类的对象，自定义类中无dispatch方法就执行View中的dispatch

3、执行View中的dispatch，利用反射执行对应的请求函数

二、 classbasedview的源码剖析

base.py

class View:

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

    @classonlymethod

    def as_view(cls, **initkwargs):

       # 实例化一个对象，对象名称为self，self是cls的对象，谁调用了cls

       # cls就是谁（当前调用cls的是BookView），

        # 所以，此时的self就是BookView的实例化对象

        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

          # 此时的request对象指向原始的request对象

           # 给self这个实例化对象赋值：原始的request

            self.request = request

            self.args = args

            self.kwargs = kwargs

           # 开始执行self.dispatch()

            return self.dispatch(request, *args, **kwargs)

        view.view_class = cls

        view.view_initkwargs = initkwargs

        update_wrapper(view, cls, updated=())

        update_wrapper(view, cls.dispatch, assigned=())

        return view

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

        if request.method.lower() in self.http_method_names:

           # 通过getattr找到的属性，已经和对象绑定了，访问的时候不需要在指明对象了

           # 不需要再：self.handler

           # 直接handler()

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

        else:

            handler = self.http_method_not_allowed

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