版本控制

版本控制

一：搭建搭建mvc模型事例

1.urls.py

from django.conf.urls import url
from django.contrib import admin
from app01 import views
urlpatterns = [
    url(r'^admin/', admin.site.urls),
    url(r'^users/$', views.UsersView.as_view()),
]

2.views.py

from rest_framework.views import APIView
from django.shortcuts import HttpResponse
from django.views import View

class UsersView(APIView):

    def get(self,request,*args,**kwargs):
        print("GET")
        return HttpResponse("GET请求")
    def post(self,request,*args,**kwargs):
        print("POST")
        return HttpResponse("POST请求")

3.页面渲染效果

二、源码剖析

1.请求进来到rest_api到url执行了as_view()方法：

as_view()

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

    view = super(APIView, cls).as_view(**initkwargs)
    view.cls = cls
    view.initkwargs = initkwargs

    # Note: session based authentication is explicitly CSRF validated,
    # all other authentication is CSRF exempt.
    
	return csrf_exempt(view)

这段代码主要是将原始的类封装在视图函数上，经过url的分发执行视图函数，为什么我们可以发送直接发送post请求也是因为该方法最后一句代码：

return csrf_exempt(view) #不需要csrf_token

2.执行视图函数---APIView:

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

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

	#第一步封装request			
    request = self.initialize_request(request, *args, **kwargs)
	
    self.request = request
    self.headers = self.default_response_headers  # deprecate?
	
	
    try:
		#第二步初始化
        self.initial(request, *args, **kwargs)
		#第三步执行我们的视图函数中对应的请求方式的函数(get,post,put,...)
        # Get the appropriate handler method
        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

        response = handler(request, *args, **kwargs)

    except Exception as exc:
        response = self.handle_exception(exc)

    self.response = self.finalize_response(request, response, *args, **kwargs)
    return self.response

在dispatch方法中执行了完成了很多工作，而版本的注册就是在封装完
request就执行的
下面就将封装request剖析：

第一步：封装request

a.进入request = self.initialize_request(request, *args, **kwargs)的中：

def initialize_request(self, request, *args, **kwargs):
    """
    Returns the initial request object.
    """

	##将传参和当前的视图封装返回
    parser_context = self.get_parser_context(request)
	
	##下面就是request中封装的方法
    return Request(
        request,
        parsers=self.get_parsers(),
        authenticators=self.get_authenticators(),
        negotiator=self.get_content_negotiator(),
        parser_context=parser_context
    )

b.封装后的request中执行有下面这些方法：

1. request
2. get_parsers()
3. get_authenticators()
4. get_content_negotiator()
5. parser_context

下面接着一个个的去查看这些方法中做了什么：

get_parsers()

    def get_parsers(self):
    """
    Instantiates and returns the list of parsers that this view can use.
    """
    return [parser() for parser in self.parser_classes]

这里就得到get_parsers() = [ parser(), ]

get_authenticators()

def get_authenticators(self):
    """
    Instantiates and returns the list of authenticators that this view can use.
    """
    return [auth() for auth in self.authentication_classes]

这里就得到get_authenticators() = [ auth(), ]

get_content_negotiator()

def get_content_negotiator(self):
    """
    Instantiate and return the content negotiation class to use.
    """
    if not getattr(self, '_negotiator', None):
        self._negotiator = self.content_negotiation_class()
    return self._negotiator

这里返回值就是self._negotiator

parser_context

def get_parser_context(self, http_request):
    """
    Returns a dict that is passed through to Parser.parse(),
    as the `parser_context` keyword argument.
    """
    # Note: Additionally `request` and `encoding` will also be added
    #       to the context by the Request object.
    return {
        'view': self,
        'args': getattr(self, 'args', ()),
        'kwargs': getattr(self, 'kwargs', {})
    }

封装了当前的view和传入的参数

上述的方法所处理的功能如下