django中APIView里的dispatch和as_view方法分析

位置：

from rest_framework.views import APIView

繼承APIView類視圖形式的路由：

path('booksapiview/', views.BooksAPIView.as_view()),  #在這個地方應該寫個函數記憶體地址

繼承APIView類的視圖函數：

from rest_framework.views import APIView

class BooksAPIView(APIView):
    def get(self):
        pass
    
    def post(self):
        pass

APIView源碼分析：

繼承了APIView的視圖函數，最終執行的是APIView里的as_view方法

@classmethod
def as_view(cls, **initkwargs):
    """
    Store the original class on the view function.

    This allows us to discover information about the view when we do URL
    reverse lookups.  Used for breadcrumb generation.
    """
    if isinstance(getattr(cls, 'queryset', None), models.query.QuerySet):
        def force_evaluation():
            raise RuntimeError(
                'Do not evaluate the `.queryset` attribute directly, '
                'as the result will be cached and reused between requests. '
                'Use `.all()` or call `.get_queryset()` instead.'
            )

        cls.queryset._fetch_all = force_evaluation

    # 1.調用APIView父類，也就是View類中的as_view方法，將其返回值view在賦值給view
    view = super().as_view(**initkwargs)
    # 2.這裡踐行了一切皆對象的原則,將cls這個視圖類給了view.cls,下麵哪個也是一樣
    view.cls = cls
    view.initkwargs = initkwargs

    # Note: session based authentication is explicitly CSRF validated,
    # all other authentication is CSRF exempt.
    # 3.這句話的意思就是以後所有繼承APIView的試圖函數都沒有csrf認證了，和View類一樣，APIview類的as_view方法最後也返回了view
    # 只不過apiview新增了去除csrf認證這裡
    return csrf_exempt(view)

註意：上述返回的view記憶體地址，需要去找dispatch方法是先去apiview里找，而不是view類中的dispatch了

apiview里的dispatch方法分析：

def dispatch(self, request, *args, **kwargs):
    """
    `.dispatch()` is pretty much the same as Django's regular dispatch,
    but with extra hooks for startup, finalize, and exception handling.
    """
    self.args = args
    self.kwargs = kwargs
    # 這裡的request是self.initialize_request這個方法返回的新的由rest_framework中的Request類實例化產生的request對象
    request = self.initialize_request(request, *args, **kwargs)
    # 又把新的request對象給了視圖函數中的request,從此,視圖函數中的request就是新的request對象了
    self.request = request
    self.headers = self.default_response_headers  # deprecate?

    try:
        # 這裡執行了apiview里的initial方法，這個方法裡面包含了三大認證模塊(重要)
        self.initial(request, *args, **kwargs)

        # Get the appropriate handler method
        # 三大認證過了之後，繼續走，這裡和view裡面差不多，通過反射得到對應請求方式的函數地址
        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

        # 將get請求或者其他請求方式執行之後的結果在給response模塊
        response = handler(request, *args, **kwargs)

    # 這裡是三大認證出異常的異常模塊
    except Exception as exc:
        response = self.handle_exception(exc)

    # 渲染模塊，對response這個相應結果在進行包裝(就是在前端看到的由rest_framework渲染出來的數據結果頁面)
    self.response = self.finalize_response(request, response, *args, **kwargs)
    # 返回該渲染模塊
    return self.response

def initial(self, request, *args, **kwargs):
    # 該方法最重要的就是下麵三句代碼
    # Ensure that the incoming request is permitted
    # 這個是認證組件
    self.perform_authentication(request)
    # 這個是許可權組件
    self.check_permissions(request)
    # 這個是頻率組件
    self.check_throttles(request)