restful（2）：视图

视图部分小结：

 # as_view()中的参数：利用参数（一个字典）来指定什么方式用什么方法来执行（哪种请求方式由哪种内部方法来执行）
 # 例如 Retrieve时，需要在对应的url中添加有名分组 "pk"：?P<pk>  ，这样 retrieve()等方法中的 get_object()方法才能取到相应的记录对象

 # 流程分析：
     1. re_path(r"^authors/$",views.AuthorModelView.as_view({"get":"list","post":"create"}),name="author"),
     2. re_path(r"^authors/$",ViewSetMixin.as_view({"get":"list","post":"create"}),name="author"),
     3. re_path(r"^authors/$",ViewSetMixin.view,name="author"),

     4. 一旦用户访问 /authos/（如 get请求）:
         ViewSetMixin.view():
             for method, action in actions.items():  # {"get":"list","post":"create"}
                 handler = getattr(self, action)  # self.list  self.create
                 setattr(self, method, handler)   # self.get = self.list   # self.post = self.create

                 # getattr(self,"get")  # self.list
                 # getattr(self,"post")  # self.create

             return self.dispatch()

         APIView.dispatch():
             if request.method.lower() in self.http_method_names:
                 handler = getattr(self, request.method.lower())

                 response = handler(request, *args, **kwargs)  # self.list()

                 return response

（1）视图初级版：

from rest_framework.views import APIView
from rest_framework.response import Response
from .models import *
from django.shortcuts import HttpResponse
from django.core import serializers

from rest_framework import serializers

class BookSerializers(serializers.ModelSerializer):
      class Meta:
          model=Book
          fields="__all__"
          #depth=1

class PublshSerializers(serializers.ModelSerializer):

      class Meta:
          model=Publish
          fields="__all__"
          depth=1

class BookViewSet(APIView):

　　 # 查看所有数据
    def get(self,request,*args,**kwargs):
        book_list=Book.objects.all()
        bs=BookSerializers(instance=book_list,many=True,context={'request': request})  # 当 BookSerializers 中有 HyperlinkedIdentityField 时，其实例化时需要加上 context={'request':request}
        return Response(bs.data)  # 要返回 bs.data

　　 # 新添加一条记录
    def post(self,request,*args,**kwargs):
        print(request.data)
　　　　 

　　　　 # 创建记录时的序列化
        bs=BookSerializers(data=request.data,many=False)
        if bs.is_valid():
            print(bs.validated_data)
            bs.save()  # .save() 中有 create() 方法
            return Response(bs.data)
        else:
            return HttpResponse(bs.errors)

class BookDetailViewSet(APIView):

    def get(self,request,pk):
        book_obj=Book.objects.filter(pk=pk).first()
        bs=BookSerializers(instance=book_obj,context={'request': request})
        return Response(bs.data)

　　 # 更新数据
    def put(self,request,pk):
        book_obj=Book.objects.filter(pk=pk).first()
        bs=BookSerializers(instance=book_obj,data=request.data,context={'request': request})  # 更新数据时的序列化
        if bs.is_valid():
            bs.save()
            return Response(bs.data)
        else:
            return HttpResponse(bs.errors)

class PublishViewSet(APIView):

    def get(self,request,*args,**kwargs):
        publish_list=Publish.objects.all()
        bs=PublshSerializers(publish_list,many=True,context={'request': request})
        return Response(bs.data)

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

        bs=PublshSerializers(data=request.data,many=False)
        if bs.is_valid():
            # print(bs.validated_data)
            bs.save()
            return Response(bs.data)
        else:
            return HttpResponse(bs.errors)

class PublishDetailViewSet(APIView):

    def get(self,request,pk):

        publish_obj=Publish.objects.filter(pk=pk).first()
        bs=PublshSerializers(publish_obj,context={'request': request})
        return Response(bs.data)

    def put(self,request,pk):
        publish_obj=Publish.objects.filter(pk=pk).first()
        bs=PublshSerializers(publish_obj,data=request.data,context={'request': request})
        if bs.is_valid():
            bs.save()
            return Response(bs.data)
        else:
            return HttpResponse(bs.errors)

（2）mixin类编写视图

from rest_framework import mixins
from rest_framework import generics

class BookViewSet(mixins.ListModelMixin,
                  mixins.CreateModelMixin,
                  generics.GenericAPIView):

    queryset = Book.objects.all()  # queryset 变量表示要接收的 queryset；queryset这个名字是固定的
    serializer_class = BookSerializers  # serializer_class 变量表示要用到的序列化的类；serializer_class 这个名字是固定的

    def get(self, request, *args, **kwargs):
        return self.list(request, *args, **kwargs)

    def post(self, request, *args, **kwargs):
        return self.create(request, *args, **kwargs)

class BookDetailViewSet(mixins.RetrieveModelMixin,
                    mixins.UpdateModelMixin,
                    mixins.DestroyModelMixin,
                    generics.GenericAPIView):
    queryset = Book.objects.all()
    serializer_class = BookSerializers

    def get(self, request, *args, **kwargs):
        return self.retrieve(request, *args, **kwargs)

    def put(self, request, *args, **kwargs):
        return self.update(request, *args, **kwargs)

    def delete(self, request, *args, **kwargs):
        return self.destroy(request, *args, **kwargs)

（3）使用通用的基于类的视图

上面通过使用mixin类，可以使用更少的代码重写这些视图，但还是可以再进一步。REST框架提供了一组已经混合好(mixed-in)的通用视图，可以通过使用它来简化我们的views.py模块

from rest_framework import mixins
from rest_framework import generics

class BookViewSet(generics.ListCreateAPIView):

    queryset = Book.objects.all()
    serializer_class = BookSerializers

class BookDetailViewSet(generics.RetrieveUpdateDestroyAPIView):
    queryset = Book.objects.all()
    serializer_class = BookSerializers

class PublishViewSet(generics.ListCreateAPIView):

    queryset = Publish.objects.all()
    serializer_class = PublshSerializers

class PublishDetailViewSet(generics.RetrieveUpdateDestroyAPIView):
    queryset = Publish.objects.all()
    serializer_class = PublshSerializers

（4）viewsets.ModelViewSet

urls.py部分：

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

urlpatterns = [
    path('admin/', admin.site.urls),
    re_path(r"^books/$",views.BookModelView.as_view({"get":"list","post":"create"})),
    re_path(r"^books/(?P<pk>\d+)/$",views.BookModelView.as_view({"get":"retrieve","put":"update","delete":"destroy"})),
    # 需要在对应的url中添加有名分组 "pk"：?P<pk>  ，这样 retrieve()等方法中的 get_object()方法才能取到相应的记录对象
    re_path(r"^publish/$",views.PublishModelView.as_view({"get":"list","post":"create"}),name="publish"),
    re_path(r"^publish/(?P<pk>\d+)/$",views.PublishModelView.as_view({"get":"retrieve","put":"update","delete":"destroy"}),name="publish_detail"),
    re_path(r"^login/$",views.LoginView.as_view(),name="login"),
]

# as_view() 是否可以加参数，取决于视图的类是否继承 ViewSetMixin

views.py部分：

from app01 import models
from app01 import serializer

from rest_framework.views import APIView
from rest_framework.response import Response
# Create your views here.

from rest_framework import viewsets

class BookModelView(viewsets.ModelViewSet):
    queryset = models.Book.objects.all()  # queryset 表示要处理的数据；queryset这个变量名是固定的
    serializer_class = serializer.BookSerializers  # serializer_class 表示 所要用到的 序列化的类；serializer_class 是固定写法

class PublishModelView(viewsets.ModelViewSet):
    queryset = models.Publish.objects.all()
    serializer_class = serializer.PublishSerializers

继承的类：

class View(object):
class APIView(View)
class GenericAPIView(views.APIView)
class GenericViewSet(ViewSetMixin,generics.GenericAPIView)
class ModelViewSet(
    mixins.CreateModelMixin,
    mixins.RetriveModelMixin,
    mixins.UpdateModelMixin,
    mixins.DestroyModelMixin,
    mixins.ListModelMixin,
    GenericViewSet
)

from rest_framework.views import APIView # ** 继承 APIView 就是要写原生的 接口（API）
from rest_framework.generics import GenericAPIView
from rest_framework.viewsets import GenericViewSet  # GenericViewSet继承的ViewSetMixin，决定了 as_view() 中能加参数
from rest_framework.viewsets import ModelViewSet  # ** ModelViewSet 继承了增删改查

补充： model类.objects.update_or_create(user=user_obj,default=...)  # 表中没有就创建，有就更新；# 返回一个元组：第一个是对象，第二个是布尔值