多对多表的增删改查与drf的分页

2024-04-09 21:17:35

类的约束
面向对象的继承
处理多对多实列
分页器
分页的另一种方式
分页出现的警告问题了解
- 总结

类的约束

继承必须继续定义不然报错

# 约束子类中必须实现f1 class Base(object):
def f1(self):
    raise NotImplementedError('必须要定义此规则')

class Foo(Base):

    def f1(self):
    print(123)

obj = Foo() 
obj.f1()

面向对象的继承

class Base(object): 
    def f1(self):
        print('base.f1') 
        self.f2()
    def f2(self):
        print('base.f2')
class Foo(Base):
    def f2(self):
    print('foo.f2')

obj = Foo() 
obj.f1()

class Base(object): 
    x1 = 123

def f1(self):
    print(self.x1)

class Foo(Base): 
    x1 = 456

obj = Foo() 
obj.f1()

class APIView(object): 
    version_class = 123
    
    def get_version(self): 
        print(self.version_class)

class UserView(APIView): 
    version_class = 666

obj = UserView() 
obj.get_version()

class APIView(object): 
    version_class = 123

    def dispatch(self,method):
        self.initial() 
        getattr(self,method)()#反射

    def initial(self):
        print(self.version_class)

class UserView(APIView): 
    version_class = 666

    def get(self): 
        print('userview.get')

obj = UserView() 
obj.dispatch('get')

结果
print(self.version_class)
print('userview.get')

class URLPathVersion(object):

    def determin_version(self): 
        return 'v1'
class APIView(object): 
    version_class = None

    def dispatch(self,method): 
        version = self.initial() 
        print(version) 
        getattr(self,method)()

    def initial(self): 
        self.process_version()

    def process_version():
        obj = self.version_class() 
        return obj.determine_version()

class UserView(APIView): 
    version_class = URLPathVersion
    
    def get(self): 
        print('userview.get')

obj = UserView() 
obj.dispatch('get')

处理多对多实列

查询单条或多条

modul

from django.db import models

class Category(models.Model):
    """
    文章分类
    """
    name = models.CharField(verbose_name='分类',max_length=32)


class Article(models.Model):
    """
    文章表
    """
    status_choices = (
        (1,'发布'),
        (2,'删除'),
    )
    status = models.IntegerField(verbose_name='状态',choices=status_choices,default=1)
    title = models.CharField(verbose_name='标题',max_length=32)
    summary = models.CharField(verbose_name='简介',max_length=255)
    content = models.TextField(verbose_name='文章内容')
    category = models.ForeignKey(verbose_name='分类',to='Category')

    tag = models.ManyToManyField(verbose_name='标签',to='Tag',null=True,blank=True)

class Tag(models.Model):
    """标签"""
    title = models.CharField(verbose_name='标签',max_length=32)

url

from django.conf.urls import url
from django.contrib import admin
from api import views
urlpatterns = [
    url(r'^new/article/$', views.NewArticleView.as_view()),
    url(r'^new/article/(?P<pk>\d+)/$', views.NewArticleView.as_view()),

]

约束展示

class NewArticleSerializer(serializers.ModelSerializer):
    tag_info = serializers.SerializerMethodField()
    
    class Meta:
        model = models.Article
        # fields = '__all__' #会自动展示
        fields = ['title','summary','tag_info']#自定义显示 必须自己加 tag_info

    def get_tag_info(self,obj):#展示的第3种方法 obj对象
        return [row for row in obj.tag.all().values('id','title')]#字典加列表的形式

    
obj.字段.all().values('要显示的字段1','要显示的字段2')

view

class NewArticleView(APIView):

    def get(self,request,*args,**kwargs):
        pk = kwargs.get('pk')
        if not pk:
            queryset = models.Article.objects.all()
            ser = serializer.NewArticleSerializer(instance=queryset,many=True)
            return Response(ser.data)
        
        article_object = models.Article.objects.filter(id=pk).first()
        ser = serializer.NewArticleSerializer(instance=article_object, many=False)
        return Response(ser.data)

    def post(self,request,*args,**kwargs):
        ser = serializer.FormNewArticleSerializer(data=request.data)
        if ser.is_valid():
            ser.save()
            return Response(ser.data)
        return Response(ser.errors)

    def put(self, request, *args, **kwargs):
        """全部更新"""
        pk = kwargs.get('pk')
        article_object = models.Article.objects.filter(id=pk).first()
        ser = serializer.FormNewArticleSerializer(instance=article_object, data=request.data)
        if ser.is_valid():
            ser.save()
            return Response(ser.data)
        return Response(ser.errors)

    def patch(self,request,*args,**kwargs):
        """局部"""
        pk = kwargs.get('pk')
        article_object = models.Article.objects.filter(id=pk).first()
        ser = serializer.FormNewArticleSerializer(instance=article_object, data=request.data,partial=True)
        if ser.is_valid():
            ser.save()
            return Response(ser.data)
        return Response(ser.errors)

    def delete(self,request,*args,**kwargs):
        pk = kwargs.get('pk')
        models.Article.objects.filter(id=pk).delete()
        return Response('删除成功')

增加编辑更新

要注意的是约束可以用不一样的为了避免展示与增加不一样

约束

class FormNewArticleSerializer(serializers.ModelSerializer):
    class Meta:
        model = models.Article
        fields = '__all__'
        
增加 编辑必须为 __all__

view

class NewArticleView(APIView):


    def post(self,request,*args,**kwargs):
        """增加"""
        ser = serializer.FormNewArticleSerializer(data=request.data)
        if ser.is_valid():
            ser.save()
            return Response(ser.data)
        return Response(ser.errors)

    def put(self, request, *args, **kwargs):
        """全部更新"""
        pk = kwargs.get('pk')
        article_object = models.Article.objects.filter(id=pk).first()
        ser = serializer.FormNewArticleSerializer(instance=article_object, data=request.data)
        if ser.is_valid():
            ser.save()
            return Response(ser.data)
        return Response(ser.errors)

    def patch(self,request,*args,**kwargs):
        """局部"""
        pk = kwargs.get('pk')
        article_object = models.Article.objects.filter(id=pk).first()
        ser = serializer.FormNewArticleSerializer(instance=article_object, data=request.data,partial=True)
        if ser.is_valid():
            ser.save()
            return Response(ser.data)
        return Response(ser.errors)

    def delete(self,request,*args,**kwargs):
        pk = kwargs.get('pk')
        models.Article.objects.filter(id=pk).delete()
        return Response('删除成功')

总结

根据业务需求不同 所以 serializers可以写多个 来应对

分页器

为什么要使用分页

其实这个不说大家都知道，大家写项目的时候也是一定会用的，

我们数据库有几千万条数据，这些数据需要展示，我们不可能直接从数据库把数据全部读取出来，

这样会给内存造成特别大的压力，有可能还会内存溢出，所以我们希望一点一点的取，

那展示的时候也是一样的，总是要进行分页显示，我们之前自己都写过分页。

那么大家想一个问题，在数据量特别大的时候，我们的分页会越往后读取速度越慢，

当有一千万条数据，我要看最后一页的内容的时候，怎么能让我的查询速度变快。

DRF给我们提供了三种分页方式，我们看下他们都是什么样的~~

分页组件的使用

DRF提供的三种分页

drf 内置分页器有几种方式只有获取多条数据时才有用

方式1

定义配置文件settings

REST_FRAMEWORK = {
    "PAGE_SIZE":2,#代表2
}

modul

原来的

url

from django.conf.urls import url
from django.contrib import admin
from api import views
urlpatterns = [
    # 分页
    url(r'^page/article/$', views.PageArticleView.as_view()),

    url(r'^page/view/article/$', views.PageViewArticleView.as_view()),
]

view

from rest_framework.pagination import PageNumberPagination
from rest_framework.pagination import LimitOffsetPagination
from rest_framework import serializers

class PageArticleSerializer(serializers.ModelSerializer):
    class Meta:
        model = models.Article
        fields = "__all__"

class PageArticleView(APIView):
    def get(self,request,*args,**kwargs):
        queryset = models.Article.objects.all()

        # 方式一：仅数据
        #分页对象
        page_object = PageNumberPagination()
        # 调用 分页对象.paginate_queryset方法进行分页，得到的结果是分页之后的数据
        # result就是分完页的一部分数据
        result = page_object.paginate_queryset(queryset,request,self)
        
        # 序列化分页之后的数据
        ser = PageArticleSerializer(instance=result,many=True)
        return Response(ser.data)

方式2

from rest_framework.pagination import PageNumberPagination
from rest_framework.pagination import LimitOffsetPagination
from rest_framework import serializers

class PageArticleSerializer(serializers.ModelSerializer):
    class Meta:
        model = models.Article
        fields = "__all__"

class PageArticleView(APIView):
    def get(self,request,*args,**kwargs):
        queryset = models.Article.objects.all()

        # 方式二：数据 + 分页信息
        page_object = PageNumberPagination()
        result = page_object.paginate_queryset(queryset, request, self)
        ser = PageArticleSerializer(instance=result, many=True)
        return page_object.get_paginated_response(ser.data)

方式3

from rest_framework.pagination import PageNumberPagination#第1种方式
from rest_framework.pagination import LimitOffsetPagination
#第2种方式
from rest_framework import serializers

class PageArticleSerializer(serializers.ModelSerializer):
    class Meta:
        model = models.Article
        fields = "__all__"

class PageArticleView(APIView):
    def get(self,request,*args,**kwargs):
        queryset = models.Article.objects.all()

     # 方式三：数据 + 部分分页信息
        page_object = PageNumberPagination()
        result = page_object.paginate_queryset(queryset, request, self)
        ser = PageArticleSerializer(instance=result, many=True)
        return Response({'count':page_object.page.paginator.count,'result':ser.data})

分页的另一种方式

from rest_framework.pagination import PageNumberPagination
from rest_framework.pagination import LimitOffsetPagination
from rest_framework import serializers

class PageArticleSerializer(serializers.ModelSerializer):
    class Meta:
        model = models.Article
        fields = "__all__"
        
#重 定义  防止 一次取过多    
class HulaLimitOffsetPagination(LimitOffsetPagination):
    max_limit = 20
        
        
class PageArticleView(APIView):
    def get(self,request,*args,**kwargs):
        queryset = models.Article.objects.all()
        
#就是类不同
        page_object = HulaLimitOffsetPagination()
        result = page_object.paginate_queryset(queryset, request, self)
        ser = PageArticleSerializer(instance=result, many=True)
        return Response(ser.data)

分页出现的警告问题了解

url

from django.conf.urls import url
from django.contrib import admin
from api import views
urlpatterns = [
    url(r'^page/view/article/$', views.PageViewArticleView.as_view()),
]

seting

REST_FRAMEWORK = {
    "PAGE_SIZE":2,#代表2
    "DEFAULT_PAGINATION_CLASS":"rest_framework.pagination.PageNumberPagination"#为什么要配置
}

view

from rest_framework.generics import ListAPIView 
class PageViewArticleSerializer(serializers.ModelSerializer):
    
    class Meta: model = models.Article 
        fields = "__all__" 
class PageViewArticleView(ListAPIView): 
    queryset = models.Article.objects.all() 
    serializer_class = PageViewArticleSerializer

总结

drf 有分页功能  对查询的数据自动分页  有3种方法

码农公寓

类的约束

面向对象的继承

处理 多对多实列

查询 单条或多条

增加 编辑 更新

总结

分页器

为什么要使用分页

方式1

方式2

方式3

分页的另一种方式

分页出现的警告问题 了解

总结

相关文章

处理多对多实列

查询单条或多条

增加编辑更新

分页出现的警告问题了解