【Django】视图之FBV与CBV

文章目录

FBV

FBV（function base views）就是在视图里使用函数处理请求。

在urls.py定义路由

from django.urls import path
from app01 import views

urlpatterns = [
    path('user/', views.user), #定义请求路由
]

在视图中处理请求

from django.shortcuts import render,HttpResponse

# Create your views here.

def user(request):
    #处理GET请求
    if request.method == 'GET':
        return HttpResponse('GET')
    
    # 处理POST请求
    if request.method == 'POST':
        return HttpResponse('POST')

CBV

CBV（class base views）就是在视图里使用类处理请求，与FBV较大的不同点就是能够根据请求的的方法自己自动执行对应的方法。

在urls.py定义路由

from django.urls import path
from app01 import views

urlpatterns = [
    path('user/', views.UserView.as_view()),
]

在视图中处理请求

from django.shortcuts import render,HttpResponse
from django.views import View

class UserView(View):

    def get(self,request,*args, **kwargs):
        # 获取数据
        return HttpResponse('GET')

    def post(self,request,*args, **kwargs):
        # 创建数据
        return HttpResponse('POST')

    def put(self,request,*args, **kwargs):
        # 更新全部数据
        return HttpResponse('put')

    def delete(self,request,*args, **kwargs):
        # 删除数据
        return HttpResponse('delete')

    def patch(self,request,*args, **kwargs):
        # 更新局部数据，例如：用户信息的name这样的某几列
        return HttpResponse('patch')

CBV源码分析

路由 -> as_view方法 -> view方法 -> dispatch方法

as_view() – – – > view()

def as_view(cls, **initkwargs):
    """Main entry point for a request-response process."""
   
         ...

    def view(request, *args, **kwargs):
        self = cls(**initkwargs)
        if hasattr(self, 'get') and not hasattr(self, 'head'):
            self.head = self.get
        self.request = request
        self.args = args
        self.kwargs = kwargs
        return self.dispatch(request, *args, **kwargs)

     ...

    return view

url(r'^test/',views.UserView.as_view()), – – – > url(r'^test/',view) =》这里就与FBV很相似了

dispatch()

上面路由走的view方法，它返回的就是dispatch方法，这样实际上执行as_view方法得到的实际上就是dispatch方法的返回值。
http_method_names = [‘get’, ‘post’, ‘put’, ‘patch’, ‘delete’, ‘head’, ‘options’, ‘trace’]

def dispatch(self, request, *args, **kwargs):
    # Try to dispatch to the right method; if a method doesn't exist,
    # defer to the error handler. Also defer to the error handler if the
    # request method isn't on the approved list.
    if request.method.lower() in self.http_method_names:
    	# 反射得到方法的函数名称
        handler = getattr(self, request.method.lower(), self.http_method_not_allowed)
    else:
        handler = self.http_method_not_allowed
    return handler(request, *args, **kwargs)  # 执行方法，拿到返回值，每个方法返回的结果是什么，就会得到什么

CBV的应用

重写dispatch方法，实现在请求之前做些操作

class UserView(View):

    def dispatch(self, request, *args, **kwargs):
        print('处理方法之前...')
        # 将方法执行的结果返回，两种调用父类的方式
        # ret = super(UserView, self).dispatch(request, *args, **kwargs)
        ret = super().dispatch(request, *args, **kwargs)
        print(ret)
        print('处理方法之后...')
        return ret

    def get(self,request,*args, **kwargs):
        #获取数据
        return HttpResponse('GET')

    def post(self,request,*args, **kwargs):
        #创建数据
        return HttpResponse('POST')

method_decorator装饰器给类的方法加装饰器

类中的方法与独立函数不完全相同，因此不能直接将函数装饰器应用于类中的方法，我们需要先将其转换为方法装饰器。Django中提供了method_decorator装饰器用于将函数装饰器转换为方法装饰器。

方式一：给某个方法加上装饰器（此例给get方法加上）

from django.views import View
from django.utils.decorators import method_decorator
  
  
class AddPublisher(View):  # CBV版
    @method_decorator(wrapper)
    def get(self, request):
        return render(request, "add_publisher.html")
  
    def post(self, request):
        pub_name = request.POST.get("name")
        models.Publisher.objects.create(name=pub_name)
        return redirect("/publisher_list/")

方式二：加在dispatch方法上面，会给类下的所有方法加上此装饰器

class AddPublisher(View):  # CBV版
    @method_decorator(wrapper)
    def dispatch(self, request, *args, **kwargs):
        obj = super(AddPublisher, self).dispatch(request, *args, **kwargs)
        return obj
  
    def get(self, request):
        return render(request, "add_publisher.html")
  
    def post(self, request):
        pub_name = request.POST.get("name")
        models.Publisher.objects.create(name=pub_name)
        return redirect("/publisher_list/")

方式三：加在类上面

@method_decorator(wrapper, name="post")
@method_decorator(wrapper, name="get")  # 给哪个方法加，就要指定name
class AddPublisher(View):  # CBV版
    def dispatch(self, request, *args, **kwargs):
        obj = super(AddPublisher, self).dispatch(request, *args, **kwargs)
        return obj
  
    def get(self, request):
        return render(request, "add_publisher.html")
  
    def post(self, request):
        pub_name = request.POST.get("name")
        models.Publisher.objects.create(name=pub_name)
        return redirect("/publisher_list/")

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