Rest framework 學習（3）基於類的視圖（CBV）

首頁，回顧一下實現接口的兩類方法FBV和CBV：

基於函數的視圖叫做FBV，基於類的視圖叫做CBV。

在API中使用CBV的優點：

1.提高了代碼的複用性（keep our code DRY），可以使用面嚮對象的技術，比如Mixin（多繼承）

2.可以用不同的函數針對不同的HTTP方法處理，而不是通過很多if判斷，提高代碼可讀性

一，類試於函數的類視圖形式：

這種模式通過APIView實現了對不同的HTTP方法分離處理，算很規範了。

from snippets.models import Snippet
from snippets.serializers import SnippetSerializer
from django.http import Http404
from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework import status


class SnippetList(APIView):
    """
    List all snippets, or create a new snippet.
    """
    def get(self, request, format=None):
        snippets = Snippet.objects.all()
        serializer = SnippetSerializer(snippets, many=True)
        return Response(serializer.data)

    def post(self, request, format=None):
        serializer = SnippetSerializer(data=request.data)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data, status=status.HTTP_201_CREATED)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)


class SnippetDetail(APIView):
    """
    Retrieve, update or delete a snippet instance.
    """
    def get_object(self, pk):
        try:
            return Snippet.objects.get(pk=pk)
        except Snippet.DoesNotExist:
            raise Http404

    def get(self, request, pk, format=None):
        snippet = self.get_object(pk)
        serializer = SnippetSerializer(snippet)
        return Response(serializer.data)

    def put(self, request, pk, format=None):
        snippet = self.get_object(pk)
        serializer = SnippetSerializer(snippet, data=request.data)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

    def delete(self, request, pk, format=None):
        snippet = self.get_object(pk)
        snippet.delete()
        return Response(status=status.HTTP_204_NO_CONTENT)

然乎修改urls.py 使其基於類的視圖

from django.urls import path
from rest_framework.urlpatterns import format_suffix_patterns
from snippets import views

urlpatterns = [
    path('snippets/', views.SnippetList.as_view()),
    path('snippets/<int:pk>/', views.SnippetDetail.as_view()),
]

urlpatterns = format_suffix_patterns(urlpatterns)

二,使用MiXin的類視圖

在這部分，MiXin是能豐富其他類能力的工具類，這裏主要使用：

ListModelMixin: self.list()   # 換回 queryset list

CreateModelMixin: self.create() 

RetrieveModelMixin: self.retrieve()   # 檢索 

UpdateModelMixin: self.update()

DestroyModelMixin: self.destroy()

from snippets.models import Snippet
from snippets.serializers import SnippetSerializer
from rest_framework import mixins
from rest_framework import generics

class SnippetList(mixins.ListModelMixin,
                  mixins.CreateModelMixin,
                  generics.GenericAPIView):
    queryset = Snippet.objects.all()
    serializer_class = SnippetSerializer

    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 SnippetDetail(mixins.RetrieveModelMixin,
                    mixins.UpdateModelMixin,
                    mixins.DestroyModelMixin,
                    generics.GenericAPIView):
    queryset = Snippet.objects.all()
    serializer_class = SnippetSerializer

    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)

三， 基於類的通用視圖

由於Rest framework 已經封裝了對MiXin的混合集成了。所以我們可以更進一步簡化代碼

from snippets.models import Snippet
from snippets.serializers import SnippetSerializer
from rest_framework import generics


class SnippetList(generics.ListCreateAPIView):
    queryset = Snippet.objects.all()
    serializer_class = SnippetSerializer


class SnippetDetail(generics.RetrieveUpdateDestroyAPIView):
    queryset = Snippet.objects.all()
    serializer_class = SnippetSerializer

總結：

CBV是我們優先考慮的API的設計方式。

從由自己去實現get,post的內部細節，到使用MiXin協助簡化代碼，到最後的直接調用集成的rest_framework.generics，不斷提高開發效率，也減少了出錯的可能。