Django中的FBV与CBV

一. FBV

FBV(function based views) 基于函数的视图, 即一个url对应一个视图函数.

1.1 FBV代码示例

urls.py

from django.contrib import admin
from django.urls import path
from app01 import views

urlpatterns = [
    path('admin/', admin.site.urls),
    path('login/',views.login)
]

views.py

from django.shortcuts import render,HttpResponse

# Create your views here.

def login(request):
    if request.method == "GET":
        return render(request,"login.html")
    else:
        if request.POST.get("user") == "afly" and request.POST.get("pwd") == "123":
            return HttpResponse("ok")
        return render(request, "login.html")

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<form action="" method="post">
    {% csrf_token %}
    用户名:<input type="text" name="user">
    密码:<input type="password" name="pwd">
    <input type="submit" value="登录">
</form>
</body>
</html>

二. CBV

CBV(class based views) 基于类的视图,即在视图里使用类处理请求.

Python是一门面向对象的变成语言, 如果只用函数来开发, 有很多面向对象的优点就用不上了(继承, 多态, 封装). 所以Django在后来加入了Class-Based-View.

可以让我们用类写View,这样做的优点主要下面两种 :

提高代码的复用性, 可以使用面向对象的技术, 例如: Mixin(多继承)
可以用不同的函数正对不同的HTTP方法处理, 而不是通过很多if判断, 提高代码可读性

2.1 CBV代码示例

urls.py

from django.contrib import admin
from django.urls import path
from app01 import views
urlpatterns = [
    path('admin/', admin.site.urls),
    path('login/', views.LoginView.as_view()),
]

views.py

from django.shortcuts import render,HttpResponse

# Create your views here.
from django.views import View
class LoginView(View):

    def get(self,request):
        return render(request,"login.html")

    def post(self,request):

        print(request.POST.get("user"))
        print(request.POST.get("pwd"))
        return HttpResponse("OK")

    def delete(self,request):

        return HttpResponse("delete...")

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>


<form action="" method="post">
    {% csrf_token %}
    用户名：<input type="text" name="user">
    密码：<input type="password" name="pwd">
    <input type="submit">
</form>
</body>
</html>

2.2 CBV的请求流程及View源码解读

1.假如有用户以get请求访问login, views.py下的LoginView会执行as_view()

2.但是LoginView类没有as_view()方法, 于是去他的父类View中查找.

3.他的父类View有此方法, as_view()中的view被执行:　

def view(request):
              
    return self.dispatch(request, *args, **kwargs)

4.view中对LoginView实例化成了self,又调用了dispatch

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

5.dispatch通过反射来判断LoginView是否有该请求方式的方法, 最后将该方法的执行结果返回