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)