drf 前戏—CBV的使用及源码流程

Posted 2022-04-04 紫青宝剑

drf 前戏—CBV的使用及源码流程

参考文献：https://www.cnblogs.com/wupeiqi/articles/7805382.html

视图：django的视图分为FBV与CBV

反射的相关知识:https://www.cnblogs.com/Blogwj123/p/15828380.html

getattr(\'对象\',\'属性名\')

1.django的CBV

urlpatterns = [
    # path(\'admin/\', admin.site.urls),
    # path(\'index/\',views.index)
    path(\'index/\',views.Index.as_view())
]

from django.shortcuts import render
from django.views import View
from django.http.response import JsonResponse

# Create your views here.
def index(request):
    ret=\'msg\':\'hello world\'
    return JsonResponse(ret)

class Index(View):
    def get(self,request):
        ret = \'msg\': \'CBV hello world\'
        return JsonResponse(ret)

2.CBV源码

• View中支持的请求方式

  # 源码中的支持方式，http的请求方式
  http_method_names = [\'get\', \'post\', \'put\', \'patch\', \'delete\', \'head\', \'options\', \'trace\']
  

• 在django的路由系统中，一个路由对应一个函数；执行父类的：as_view()

  @classonlymethod
  def as_view(cls, **initkwargs):
      """Main entry point for a request-response process."""
      for key in initkwargs:
          \'\'\'查看文件\'\'\'
      def view(request, *args, **kwargs):
          self = cls(**initkwargs)# 实例化Index对象
          self.setup(request, *args, **kwargs)
          if not hasattr(self, \'request\'):
              raise AttributeError(
                  "%s instance has no \'request\' attribute. Did you override "
                  "setup() and forget to call super()?" % cls.__name__
              )
          return self.dispatch(request, *args, **kwargs) #执行dispatch方法
      view.view_class = cls
      view.view_initkwargs = initkwargs
  
      update_wrapper(view, cls, updated=())
      update_wrapper(view, cls.dispatch, assigned=())
      return view #返回函数view
  

  说明：通过执as_view()每个视图函数都会执行dispatch()方法。

  def dispatch(self, request, *args, **kwargs):
      \'\'\'源码\'\'\'
      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
      return handler(request, *args, **kwargs)
  

3.扩展源码功能

说明：当子类没有方法时执行父类的，子类有值的时候执行子类（当前对象）的方法。

class Index(View):
    def dispatch(self, request, *args, **kwargs):
        return HttpResponse("dispatch") # 返回dispatch
    def get(self,request,*args,**kwargs):
        self.dispatch()
        ret = \'msg\': \'CBV hello world\'
        return JsonResponse(ret)

# Create your views here.
def index(request):
    ret=\'msg\':\'hello world\'
    if request.method==\'POST\':#request.method会把请求字母变化为大写
        pass
    return JsonResponse(ret)

class Index(View):
    def dispatch(self, request, *args, **kwargs):
        \'\'\'自定义dispatch\'\'\'
        func=getattr(self,request.method.lower())# self相当于对象。request.menthod获取当前请求的方式,使用反射
        ret=func(request,*args,**kwargs) # 加括号执行改函数,
        return ret
    def get(self,request,*args,**kwargs):
        # self.dispatch()
        ret = \'msg\': \'CBV hello world\'
        return JsonResponse(ret)

def dispatch(self, request, *args, **kwargs):
    print("执行前")
    ret=super(Index,self).dispatch(request, *args, **kwargs)
    print("执行后")
    return ret

from django.shortcuts import render,HttpResponse
from django.views import View
from django.http.response import JsonResponse


# Create your views here.

class MyBaseView(object):
    def dispatch(self, request, *args, **kwargs):
        print("执行前")
        ret=super(Index,self).dispatch(request, *args, **kwargs)
        # super()指当前对象父类,并不是某个类的父类，抽取出来可以供其他类的视图调用
        print("执行后")
        return ret

def index(request):
    ret=\'msg\':\'hello world\'
    if request.method==\'POST\':#request.method会把请求字母变化为大写
        pass
    return JsonResponse(ret)

class Index(MyBaseView,View):
    def get(self,request,*args,**kwargs):
        # self.dispatch()
        ret = \'msg\': \'CBV hello world\'
        return JsonResponse(ret)

class StudentView(MyBaseView,View):
    \'\'\'
    MyBaseView写在左边才会生效，因为View中存在默认的dispatch()方法。
    	面向对象中多继承左面优先(特殊情况下按照C3算法的进行继承)
    \'\'\'
    pass

4.使用django开发接口

• 根据method不同做不同的操作；

4.1 基于FBV开发

urlpatterns = [
	re_path(r\'^order/\', views.order),
]
# 根据不同的请求方式完成不同的操作
def order(request):
    if request.method == \'GET\':
    	return HttpResponse(\'获取订单\')
    elif request.method == \'POST\':
    	return HttpResponse(\'创建订单\')
    elif request.method == \'PUT\':
    	return HttpResponse(\'更新订单\')
    elif request.method == \'DELETE\':
    	return HttpResponse(\'删除订单\')

4.2 基于CBV

urlpatterns = [
	re_path(r\'^order/\', views.OrderView.as_view()),
]
# 根据不同的请求方式完成不同的操作
class OrderView(View):
    def get(self,request,*args,**kwargs):
    	return HttpResponse(\'获取订单\')

    def post(self,request,*args,**kwargs):
    	return HttpResponse(\'创建订单\')

    def put(self,request,*args,**kwargs):
    	return HttpResponse(\'更新订单\')
    
    def delete(self,request,*args,**kwargs):
    	return HttpResponse(\'删除订单\')

说明：推荐使用CBV进行开发。

5.drf 引入

5.1 安装

pip install djangorestframework

5.2 介绍

• REST与技术无关，代表的是一种软件架构风格，REST是Representational State Transfer的简称，中文翻译为表征状态转移。
• REST从资源的角度类审视整个网络，它将分布在网络中某个节点的资源通过URL进行标识，客户端应用通过URL来获取资源的表征，获得这些表征致使这些应用转变状态;
• 所有的数据，不过是通过网络获取的还是操作(增删改查)的数据，都是资源，将一切数据视为资源是REST区别与其他架构风格的最本质属性;
• 对于REST这种面向资源的架构风格，有人提出一种全新的结构理念，即：面向资源架构（ROA：Resource Oriented Architecture）

继续努力，终成大器！