DjangoRestFramework study of two sequences of assembly, assembly view

DjangoRestFramework study of two sequences of assembly, assembly view

Contents of this section

A serialization component

　　First, in accordance with the specifications we create some restful api interfaces, write Follow these forms it:

　　　　Courses --- GET ---> Data View -----> returns all data list [{}, {},]

　　　　Courses --- POST ---> add data -----> {} return data added

　　　　courses / 1 --- PUT ---> pk update data = 1 -----> returns the updated data {}

　　　　courses / 1 --- DELETE ---> Delete data pk = 1 -----> return null

　　　　courses / 1 --- GET ---> single view of data -----> Returns a single data {}

　　In this way, we look at a page similar to a drf Postman functionality we offer, we first create a django project, create a Course table, and then add some data, and then follow the steps below,

　　　　The first step: the introduction of the Response object drf　　

from django.shortcuts import render,HttpResponse,redirect
import json
from django.views import View
from app01 import models
from rest_framework.views import APIView

#引用drf提供的Response对象
from rest_framework.response import Response
#写我们的CBV视图
class CourseView(APIView):
　　#返回所有的Course数据
    def get(self,request):
        course_obj_list = models.Course.objects.all()
        ret = []
        for course_obj in course_obj_list:
            ret.append({
                "title":course_obj.title,
                "desc":course_obj.desc,
            })
        # return HttpResponse(json.dumps(ret, ensure_ascii=False))
        return Response(json.dumps(ret, ensure_ascii=False)) #这里使用Response来返回消息

    def post(self,request):
        print(request.data)
        return HttpResponse('POST')

　　　　Step Two: Configure App, our configuration settings in the configuration file

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'app01.apps.App01Config',
    'rest_framework',  #将它注册成App
]

　　　　The third step is to configure our route

"""
from django.conf.urls import url
from django.contrib import admin
from app01 import views
urlpatterns = [
    url(r'^admin/', admin.site.urls),
    url(r'^courses/', views.CourseView.as_view(),name='courses'),
]

　　　　Step Four: Start project, visit our route through the browser (browser must be accessed to see the corresponding function) to see results:

　　　　　　

　　　　That which we can send different types of requests, see the corresponding return data, similar to the Postman, but not Postman easy to use, so we use Postman after debugging tool, but we know what expensive.

　　The above data, we serialize themselves via the json, in fact django also provides us with a simple sequence of components, to see usage:

from django.shortcuts import render,HttpResponse,redirect
import json
from django.views import View
from app01 import models
from rest_framework.views import APIView
from django.core.serializers import serialize  #django的序列化组件，不是我们要学的drf的序列化组件昂

#不用json自己来序列化了，太麻烦，我们使用drf提供的序列化组件
from rest_framework.response import Response

class CourseView(APIView):

    def get(self,request):
        course_obj_list = models.Course.objects.all()
        # ret = []
        # for course_obj in course_obj_list:
        #     ret.append({
        #         "title":course_obj.title,
        #         "desc":course_obj.desc,
        #     })
        # return HttpResponse(json.dumps(ret, ensure_ascii=False))
        # return Response(json.dumps(ret, ensure_ascii=False)
        se_data = serialize('json',course_obj_list,ensure_ascii=False)
        print(se_data)#也拿到了序列化之后的数据，简洁很多
        #[{"model": "app01.course", "pk": 1, "fields": {"title": "python", "desc": "666"}}, {"model": "app01.course", "pk": 2, "fields": {"title": "linux", "desc": "\u4e5f\u5f88\u597d"}}, {"model": "app01.course", "pk": 3, "fields": {"title": "go", "desc": "\u5c06\u6765\u53ef\u80fd\u5f88\u597d"}}]

        return Response(se_data)

　　Then we know that the two serialization, this serialization is not it much simpler ah, but drf gave us a more serialized fast hardware components, more powerful, and not only do serialization, but also serialized components do other things, so, do api, we still use drf provided.

import json
from datetime import datetime
from datetime import date

#对含有日期格式数据的json数据进行转换
class JsonCustomEncoder(json.JSONEncoder):
    def default(self, field):
        if isinstance(field,datetime):
            return field.strftime('%Y-%m-%d %H:%M:%S')
        elif isinstance(field,date):
            return field.strftime('%Y-%m-%d')
        else:
            return json.JSONEncoder.default(self,field)


d1 = datetime.now()

dd = json.dumps(d1,cls=JsonCustomEncoder)
print(dd)

　　Next to focus on, and we play with data serialization component drf provided:

　　1. We GET method, to see all the data Course.

from django.shortcuts import render,HttpResponse,redirect
import json
from django.views import View
from app01 import models
from rest_framework.views import APIView
from django.core.serializers import serialize  #django的序列化组件，不是我们要学的drf的序列化组件昂
#from rest_framework import status #返回指定状态码的时候会用到
#return Response(se_data，status=status=HTTP_400_BAD_REQUEST)
#或者这种方式返回来指定状态码：return JsonResponse(serializer.data, status=201)
from rest_framework.response import Response

# 序列化方式3，1.引入drf序列化组件
from rest_framework import serializers

# 2.首先实例化一个类，继承drf的serializers.Serializer，类似于我们的form组件和models的用法
class CourseSerializers(serializers.Serializer):
    #这里面也要写对应的字段，你写了哪些字段，就会对哪些字段的数据进行序列化，没有被序列化的字段，不会有返回数据，你可以注释掉一个，然后看返回的数据是啥
    title = serializers.CharField(max_length=32，required=False) #序列化的时候还能校验字段
    desc = serializers.CharField(max_length=32)

class CourseView(APIView):

    def get(self,request):
        course_obj_list = models.Course.objects.all()
        # 3.使用我们创建的序列化类
        cs = CourseSerializers(course_obj_list, many=True)  # 序列化多个对象的时候，需要些many=True参数
        #4.通过返回对象的data属性就能拿到序列化之后的数据
        se_data = cs.data
        print(se_data) #[OrderedDict([('title', 'python'), ('desc', '666')]), OrderedDict([('title', 'linux'), ('desc', '也很好')]), OrderedDict([('title', 'go'), ('desc', '将来可能很好')])] 列表嵌套的有序字典。

        #还记得创建字典的另外一种写法吗？这个没啥用昂，给大家回顾一下之前的知识
        # d1 = {'name':'chao'}
        # d2 = dict([('name','chao'),('age',18)])
        # print(d1) #{'name': 'chao'}
        # print(d2) #{'age': 18, 'name': 'chao'}
        # # 有序字典
        # from collections import OrderedDict
        # d3 = OrderedDict([('name','Jaden'),('age',22)])
        # print(d3) #OrderedDict([('name', 'Jaden'), ('age', 22)])

        return Response(se_data) #drf的Response如果返回的是drf序列化之后的数据，那么客户端拿到的是一个有格式的数据，不再是一行显示了

　　See results:

　　　　

　　2. to add a data POST method:

from django.shortcuts import render,HttpResponse,redirect
from django.views import View
from app01 import models
from rest_framework.views import APIView

from rest_framework.response import Response

from rest_framework import serializers

class CourseSerializers(serializers.Serializer):
    title = serializers.CharField(max_length=32)
    desc = serializers.CharField(max_length=32)

class CourseView(APIView):

    def get(self,request):
        course_obj_list = models.Course.objects.all()
        cs = CourseSerializers(course_obj_list, many=True)
        se_data = cs.data
        return Response(se_data)

    def post(self,request):
        # print(request.data) #{'desc': 'java也挺好', 'title': 'java'}
        #发送过来的数据是不是要进行验证啊，drf的序列化组件还能校验数据
        cs = CourseSerializers(data=request.data,many=False) #注意必须是data=这种关键字参数,注意，验证单条数据的时候写上many=False参数,而且我们还要序列化这个数据，因为我们要给客户端返回这个数据
        # print(cs.is_valid()) #True ，如果少数据，得到的是False
        if cs.is_valid():
            print(cs.data)
            models.Course.objects.create(**cs.data)#添加数据
            return Response(cs.data) #按照post添加数据的api规则，咱们要返回正确的数据
        else:
            # 假如客户端发送过来的数据是这样的，少title的数据
            # {
            #     "desc": "java也挺好"
            # }
            cs_errors = cs.errors
            # print(cs_errors) #{'title': ['This field is required.']}
            return Response(cs_errors)
            # postman上我们看到的效果是下面这样的
            # {
            #     "title": [
            #         "This field is required."
            #     ]
            # }

　　Then add some data, good, let's play some table has any relationship

class Author(models.Model): 
    nid = models.AutoField(primary_key=True)
    name=models.CharField( max_length=32)
    age=models.IntegerField()

class AuthorDetail(models.Model):

    nid = models.AutoField(primary_key=True)
    birthday=models.DateField()
    telephone=models.BigIntegerField()
    addr=models.CharField( max_length=64)

class Publish(models.Model):
    nid = models.AutoField(primary_key=True)
    name=models.CharField( max_length=32)
    city=models.CharField( max_length=32)
    email=models.EmailField()

class Book(models.Model):

    nid = models.AutoField(primary_key=True)
    title = models.CharField( max_length=32)
    publishDate=models.DateField()
    price=models.DecimalField(max_digits=5,decimal_places=2)
    publish=models.ForeignKey(to="Publish",to_field="nid",on_delete=models.CASCADE) #多对一到Publish表
    authors=models.ManyToManyField(to='Author',) #多对多到Author表

　　See serialization code:　

from django.shortcuts import render,HttpResponse,redirect
from django.views import View
from app01 import models

from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework import serializers


class BookSerializers(serializers.Serializer):
    #我们先序列化写两个字段的数据，别忘了这里面的字段和model表中的字段变量名要一样
    title = serializers.CharField(max_length=32)
    price = serializers.DecimalField(max_digits=5, decimal_places=2)

    #一对多的处理
    # publish = serializers.CharField(max_length=32)  #返回对象
    publish_email = serializers.CharField(max_length=32, source='publish.email')  # source指定返回的多对一的那个publish对象的email数据，并且我们现在找到书籍的email，所以前面的字段名称就可以不和你的publish对应好了，随便取名字
    publish_name = serializers.CharField(max_length=32, source='publish.name')  # source指定返回的多对一的那个publish对象的其他字段数据，可以接着写字段,也就是说关联的所有的字段的数据都可以写在这里进行序列化

    #对多对的处理
    # authors = serializers.CharField(max_length=32) #bookobj.authors拿到的类似于一个models.Authors.object，打印的时候这是个None
    # authors = serializers.CharField(max_length=32,source="authors.all") #这样写返回的是queryset类型的数据，这样给前端肯定是不行的，所以按照下面的方法写
    authors = serializers.SerializerMethodField() #序列化方法字段，专门给多对多字段用的，然后下面定义一个方法，方法名称写法是这样的get_字段名,名字必须是这样
    def get_authors(self,obj): #参数写一个obj，这个obj是一个一个的书籍对象，然后我们通过书籍对象来返回对应的数据
        # author_list_values = obj.authors.all().values() #返回这样类型的数据也行,那么具体你要返回什么结构的数据，需要和前端人员沟通清楚，然后这里对数据进行加工
        #假如加工成的数据是这种类型的[ {},{} ],就可以按照下面的逻辑来写，我简单写的，肯定有更好的逻辑来加工这些数据
        author_list_values = []
        author_dict = {}
        author_list = obj.authors.all()
        for i in author_list:
            author_dict['name'] = i.name
            author_list_values.append(author_dict)
        return author_list_values


class BookView(APIView):
    def get(self,request):
        book_obj_list = models.Book.objects.all()
        s_books = BookSerializers(book_obj_list,many=True)
        return Response(s_books.data)

    def post(self,request):
        pass

　　In fact, within the serializer to do this simple thing, expensive pseudo-code.

　　　　

　　urls.py is written like this:

urlpatterns = [
    #url(r'^admin/', admin.site.urls),
    #做一些针对书籍表的接口
    url(r'^books/', views.BookView.as_view(),),

]

　　Then look at the data Postman returned:

　　　　

　　Then we will be able to complete the sequence of various data, but you will find, too tired to write it, it's just a table ah, if hundreds of tables zezheng ah, so there is a simpler way (similar to in form and modelform difference).

　　We use ModelSerializer, look at the code:

#ModelSerializer
class BookSerializers(serializers.ModelSerializer):
    class Meta:
        model=models.Book
        # fields=['title','price','publish','authors']
        fields = "__all__"
        # 如果直接写all，你拿到的数据是下面这样的，但是如果人家前端和你要的作者的id和名字，你是不是要处理一下啦
        # [
        #     {
        #         "nid": 3,
        #         "title": "go",
        #         "publishDate": null,
        #         "price": "122.00",
        #         "publish": 2,
        #         "authors": [
        #             2,
        #             1
        #         ]
        #     }
        # ]
    #那么没办法，只能自己再进行加工处理了，按照之前的方式
    authors = serializers.SerializerMethodField()
    def get_authors(self,obj):
        author_list_values = []
        author_dict = {}
        author_list = obj.authors.all()
        for i in author_list:
            author_dict['id'] = i.pk
            author_dict['name'] = i.name
            author_list_values.append(author_dict)
        return author_list_values #这个数据就会覆盖上面的序列化的authors字段的数据
    # 那么前端拿到的数据就这样了
    # [
    #     {
    #         "nid": 3,
    #         "authors": [
    #             {
    #                 "name": "chao",
    #                 "id": 1
    #             },
    #             {
    #                 "name": "chao",
    #                 "id": 1
    #             }
    #         ],
    #         "title": "go",
    #         "publishDate": null,
    #         "price": "122.00",
    #         "publish": 2
    #     }
    # ]
    # 那如果一对多关系的那个publish，前端想要的数据是名字怎么办呢？还是老办法，source
    # publish_name = serializers.CharField(max_length=32, source='publish.name')#但是你会发现序列化之后的数据有个publish:1对应个id值，如果我不想要他怎么办，那么可以起个相同的变量名来覆盖它，比如下面的写法
    publish = serializers.CharField(max_length=32, source='publish.name')

class BookView(APIView):
    def get(self,request):
        book_obj_list = models.Book.objects.all()
        s_books = BookSerializers(book_obj_list,many=True)
        return Response(s_books.data)

    def post(self,request):
        pass

　　Above we completed the get request to see all the information about books, then we play a post request to add a book data, directly on the bar code:

class BookSerializers(serializers.ModelSerializer):
    class Meta:
        model=models.Book
        fields = "__all__"
　　 # 注意先把下面这些注释掉,不然由于get和post请求我们用的都是这个序列化组件，会出现多对多变量冲突的问题，所以一般都将读操作和写操作分成两个序列化组件来写
    # authors = serializers.SerializerMethodField() #也可以用来处理一对多的关系字段
    # def get_authors(self,obj):
    #     author_list_values = []
    #     author_dict = {}
    #     author_list = obj.authors.all()
    #     for i in author_list:
    #         author_dict['id'] = i.pk
    #         author_dict['name'] = i.name
    #         author_list_values.append(author_dict)
    #     return author_list_values
    # publish = serializers.CharField(max_length=32, source='publish.name')

class BookView(APIView):
    def get(self,request):
        book_obj_list = models.Book.objects.all()
        s_books = BookSerializers(book_obj_list,many=True)
        return Response(s_books.data)


    def post(self,request):

        b_serializer = BookSerializers(data=request.data,many=False)
        if b_serializer.is_valid():
            print('xxxx')
            b_serializer.save() #因为这个序列化器我们用的ModelSerializer，并且在BookSerializers类中我们指定了序列化的哪个表，所以直接save，它就知道我们要将数据保存到哪张表中,其实这句话执行的就是个create操作。
            return Response(b_serializer.data) #b_serializer.data这就是个字典数据

        else:
            return Response(b_serializer.errors)

​

　　We finished writing the above interfaces GET and POST requests, let's complete PUT, DELETE, GET single interface to view several data.

#一个读序列化组件，一个写序列化组件
class BookSerializers1(serializers.ModelSerializer):
    class Meta:
        model=models.Book
        fields = "__all__"
    def create(self, validated_data):
        print(validated_data)
        #{'publishDate': datetime.date(2012, 12, 12), 'publish': <Publish: Publish object>, 'authors': [<Author: Author object>, <Author: Author object>], 'title': '老酒3', 'price': Decimal('15.00')}
        authors = validated_data.pop('authors')
        obj = models.Book.objects.create(**validated_data)
        obj.authors.add(*authors)
        return obj

class BookSerializers2(serializers.ModelSerializer):
    class Meta:
        model=models.Book
        fields = "__all__"

    authors = serializers.SerializerMethodField()
    def get_authors(self,obj):
        print('sssss')
        author_list_values = []
        author_dict = {}
        author_list = obj.authors.all()
        for i in author_list:
            author_dict['id'] = i.pk
            author_dict['name'] = i.name
            author_list_values.append(author_dict)
        return author_list_values
    publish = serializers.CharField(max_length=32, source='publish.name')


class BookView(APIView):
    def get(self,request):
        book_obj_list = models.Book.objects.all()
        s_books = BookSerializers2(book_obj_list,many=True)
        return Response(s_books.data)

    def post(self,request):
        b_serializer = BookSerializers1(data=request.data,many=False)
        if b_serializer.is_valid():
            print('xxxx')
            b_serializer.save() 
            return Response(b_serializer.data) 

        else:
            return Response(b_serializer.errors)

　　urls.py reads as follows:

from django.conf.urls import url
from django.contrib import admin
from app01 import views
urlpatterns = [
    url(r'^admin/', admin.site.urls),
    # url(r'^courses/', views.CourseView.as_view()),
    #做一些针对书籍表的接口
    #GET和POST接口的url
    url(r'^books/$', views.BookView.as_view(),), #别忘了$符号结尾

    #PUT、DELETE、GET请求接口
    url(r'^books/(\d+)/', views.SBookView.as_view(),),

]

　　views.py code is as follows:

from django.shortcuts import render,HttpResponse,redirect
from django.views import View
from app01 import models

from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework import serializers

class BookSerializers(serializers.ModelSerializer):
    class Meta:
        model=models.Book
        fields = "__all__"

class BookView(APIView):
    def get(self,request):
        '''
        查看所有书籍
        :param request:
        :return:
        '''
        book_obj_list = models.Book.objects.all()
        s_books = BookSerializers(book_obj_list,many=True)
        return Response(s_books.data)

    def post(self,request):
        '''
        添加一条数据
        :param request:
        :return:
        '''
        b_serializer = BookSerializers(data=request.data,many=False)
        if b_serializer.is_valid():
            b_serializer.save()
            return Response(b_serializer.data)
        else:
            return Response(b_serializer.errors)

#因为更新一条数据，删除一条数据，获取一条数据，都有个单独的参数(获取一条数据的，一般是id，所以我将put、delete、get写到了一个视图类里面，也就是说结合上面那个BookView视图类，完成了我们的那些接口)
class SBookView(APIView):
    def get(self,request,id):
        '''
        获取单条数据
        :param request:
        :param id:
        :return:
        '''
        book_obj = models.Book.objects.get(pk=id)#获取这条数据对象
        #接下来序列化单个model对象，序列化单个对象返回的是一个字典结构 {},序列化多个对象返回的是[{},{}]这种结构
        book_serializer = BookSerializers(book_obj,many=False)
        return Response(book_serializer.data)


    def put(self,request,id):
        '''
        更新一条数据
        :param request:request.data更新提交过来的数据
        :param id:
        :return:
        '''
        book_obj = models.Book.objects.get(pk=id)
        b_s = BookSerializers(data=request.data,instance=book_obj,many=False) #别忘了写instance,由于我们使用的ModelSerializer，所以前端提交过来的数据必须是所有字段的数据，当然id字段不用
        if b_s.is_valid():
            b_s.save() #翻译成的就是update操作
            return Response(b_s.data) #接口规范要求咱们要返回更新后的数据
        else:
            return Response(b_s.errors)

    def delete(self,request,id):
        '''
        删除一条数据
        :param request:
        :param id:
        :return:
        '''
        book_obj = models.Book.objects.get(pk=id).delete()
        return Response("") #别忘了接口规范说最好返回一个空

　　Well, five interfaces finished, even if we serialization component is finished, do not forget to see the last of that hole this section.

　　

　　Rewrite the create method save

class BookSerializers(serializers.ModelSerializer):

      class Meta:
          model=Book
          fields="__all__"
          # exclude = ['authors',]
          # depth=1

      def create(self, validated_data):
        
          authors = validated_data.pop('authors')
          obj = Book.objects.create(**validated_data)
          obj.authors.add(*authors)
          return obj

　　Hyperlinks API, Hyperlinked

class BookSerializers(serializers.ModelSerializer):
      publish= serializers.HyperlinkedIdentityField(
                     view_name='publish_detail',
                     lookup_field="publish_id",
                     lookup_url_kwarg="pk")
      class Meta:
          model=Book
          fields="__all__"
          #depth=1

　　serializer properties and methods:

1.save()
在调用serializer.save()时，会创建或者更新一个Model实例(调用create()或update()创建)，具体根据序列化类的实现而定，如：

2.create()、update()
Serializer中的create()和update()方法用于创建生成一个Model实例，在使用Serializer时，如果要保存反序列化后的实例到数据库，则必须要实现这两方法之一，生成的实例则作为save()返回值返回。方法属性validated_data表示校验的传入数据，可以在自己定义的序列化类中重写这两个方法。

3. is_valid()
当反序列化时，在调用Serializer.save()之前必须要使用is_valid()方法进行校验，如果校验成功返回True，失败则返回False，同时会将错误信息保存到serializer.errors属性中。

4.data
serializer.data中保存了序列化后的数据。

5.errors
当serializer.is_valid()进行校验后，如果校验失败，则将错误信息保存到serializer.errors属性中。

　　serializer的Field：

1.CharField
对应models.CharField,同时如果指定长度，还会负责校验文本长度。

max_length:最大长度；
min_length:最小长度；
allow_blank=True:表示允许将空串做为有效值，默认False；

2.EmailField
对应models.EmailField,验证是否是有效email地址。

3.IntegerField
对应models.IntegerField,代表整数类型

4.FloatField
对应models.FloatField,代表浮点数类型

5.DateTimeField
对应models.DateTimeField,代表时间和日期类型。

format='YYYY-MM-DD hh:mm':指定datetime输出格式，默认为DATETIME_FORMAT值。
需要注意，如果在 ModelSerializer 和HyperlinkedModelSerializer中如果models.DateTimeField带有auto_now=True或者auto_add_now=True，则对应的serializers.DateTimeField中将默认使用属性read_only=True,如果不想使用此行为，需要显示对该字段进行声明：

    class CommentSerializer(serializers.ModelSerializer):
        created = serializers.DateTimeField()
     
        class Meta:
            model = Comment
        
6.FileField
对应models.FileField，代表一个文件，负责文件校验。

max_length:文件名最大长度；
allow_empty_file：是否允许为空文件；

7.ImageField
对应models.ImageField，代表一个图片，负责校验图片格式是否正确。

max_length:图片名最大长度；
allow_empty_file：是否允许为空文件；
如果要进行图片处理，推荐安装Pillow: pip install Pillow

8.HiddenField
这是serializers中特有的Field，它不根据用户提交获取值，而是从默认值或可调用的值中获取其值。一种常见的使用场景就是在Model中存在user_id作为外键，在用户提交时，不允许提交user_id,但user_id在定义Model时又是必须字段，这种情况下就可以使用HiddenField提供一个默认值：

    class LeavingMessageSerializer(serializers.Serializer):
        user = serializers.HiddenField(
            default=serializers.CurrentUserDefault()
        )

　　serializer common parameters:

所谓公共参数，是指对于所有的serializers.<FieldName>都可以接受的参数。以下是常见的一些公共参数。

1.read_only
    read_only=True表示该字段为只读字段，即对应字段只用于序列化时(输出)，而在反序列化时(创建对象)不使用该字段。默认值为False。

2.write_only
    write_only=True表示该字段为只写字段，和read_only相反，即对应字段只用于更新或创建新的Model时，而在序列化时不使用，即不会输出给用户。默认值为False。

3.required
    required=False表示对应字段在反序列化时是非必需的。在正常情况下，如果反序列化时缺少字段，则会抛出异常。默认值为True。

4.default
    给字段指定一个默认值。需要注意，如果字段设置了default，则隐式地表示该字段已包含required=False，如果同时指定default和required，则会抛出异常。

5.allow_null
    allow_null=True表示在序列化时允许None作为有效值。需要注意，如果没有显式使用default参数，则当指定allow_null=True时，在序列化过程中将会默认default=None,但并不会在反序列化时也默认。

6.validators
    一个应用于传入字段的验证函数列表，如果验证失败，会引发验证错误，否则直接是返回，用于验证字段，如：

    username = serializers.CharField(max_length=16, required=True, label='用户名',
                                    validators=[validators.UniqueValidator(queryset=User.objects.all(),message='用户已经存在')])　

7.error_message
    验证时错误码和错误信息的一个dict，可以指定一些验证字段时的错误信息，如：

    mobile= serializers.CharField(max_length=4, required=True, write_only=True, min_length=4,
                                 label='电话', error_messages={
                                    'blank': '请输入验证码',
                                    'required': '该字段必填项',
                                    'max_length': '验证码格式错误',
                                    'min_length': '验证码格式错误',
                                })
7.style
    一个键值对，用于控制字段如何渲染，最常用于对密码进行密文输入，如：

    password = serializers.CharField(max_length=16, min_length=6, required=True, label='密码',
                                    error_messages={
                                        'blank': '请输入密码',
                                        'required': '该字段必填',
                                        'max_length': '密码长度不超过16',
                                        'min_length': '密码长度不小于6',
 
                                    },
                                    style={'input_type': 'password'}, write_only=True)　
9.label
    一个简短的文本字串，用来描述该字段。

10.help_text
    一个文本字串，可用作HTML表单字段或其他描述性元素中字段的描述。

11.allow_blank
    allow_blank=True 可以为空    设置False则不能为空

12.source
    source='user.email'(user表的email字段的值给这值)  设置字段值  类似default   通常这个值有外键关联属性可以用source设置

13.validators
    验证该字段跟  单独的validate很像

    UniqueValidator 单独唯一

    validators=[UniqueValidator(queryset=UserProfile.objects.all())

    UniqueTogetherValidator: 多字段联合唯一，这个时候就不能单独作用于某个字段，我们在Meta中设置。

    validators = [UniqueTogetherValidator(queryset=UserFav.objects.all(),fields=('user', 'course'),message='已经收藏')]

14.error_messages
    错误消息提示

    error_messages={
        "min_value": "商品数量不能小于一",
        "required": "请选择购买数量"
    })
7.ModelSerializers
    ModelSerializers继承于Serializer，相比其父类，ModelSerializer自动实现了以下三个步骤：

    1.根据指定的Model自动检测并生成序列化的字段，不需要提前定义；
    2.自动为序列化生成校验器；
    3.自动实现了create()方法和update()方法。
    使用ModelSerializer方式如下：

    class StudentSerializer(serializers.ModelSerializer):
        class Meta:
            # 指定一个Model，自动检测序列化的字段
            model = StudentSerializer
            fields = ('id', 'name', 'age', 'birthday')
相比于Serializer，可以说是简单了不少，当然，有时根据项目要求，可能也会在ModelSerializer中显示声明字段，这些在后面总结。

model
该属性指定一个Model类，ModelSerializer会根据提供的Model类自动检测出需要序列化的字段。默认情况下，所有Model类中的字段将会映射到ModelSerializer类中相应的字段。

　　About the same sequence of components do get (obtain data) and post (add data) when the number of pits , directly on the bar code (such as in-depth look at me, and then give a better answer ~~):

class BookSerializers(serializers.ModelSerializer):

    class Meta:
        model=models.Book
        fields = "__all__"
        # 下面这个extra_kwargs暂时忽略
        # extra_kwargs = {
        #     # 'publish': {'write_only': True},  #让publish和authors字段的数据只往数据库里面写，但是查询展示的时候，不显示这两个字段，因为我们下面配置了publish要返回的数据叫做publish_name
        #     # 'authors': {'write_only': True}
        # }    #read_only属性的意思是，这个字段名称的数据只能查看，不保存，如果用户提交的数据中有这个字段的数据，将会被剔除。
    #在我们的BookSerializers类下面可以重写create和update方法，但是validated_data这个数据是在用户提交完数据过来，并且经过序列化校验之后的数据，序列化校验除了一些required等基础校验之外，还会会根据咱们写的这个序列化组件中设置的字段中有read_only=True属性的字段排除掉，这也是为什么我们在面写多对多和一对多字段时，如果字段名称和model表中多对多或者一对多的字段名称相同，那么用户提交过来的数据中以这个字段命名的数据会被剔除，那么validated_data里面就没有多对多和一对多字段的数据了，那么再执行create方法的时候validated_data.pop('authors')这里就会报错，说找不到authors属性。
    # def create(self, validated_data):
    #     print(validated_data)
    #     authors = validated_data.pop('authors')
    #     for i in authors:
    #         print(i.pk)
    #     obj = models.Book.objects.create(**validated_data)
    #     obj.authors.add(*authors)
    #     return obj

    authors_list = serializers.SerializerMethodField() #注意，当你用这个序列化组件既做查询操作，又做添加数据的操作，那么这个字段的名字不能和你models中多对多字段的名字相同，这里也就不能叫做authors
    # authors = serializers.SerializerMethodField()
    # authors_list = A() #报错：{"authors_list": ["This field is required."]}，也就是说，如果我们将SerializerMethodField中的read_only改成False，那么在进行字段验证的时候，这个字段就没有被排除，也就是说，必须传给我这个authors_list名字的数据，但是如果我们前端给的数据中添加了这么一个数据authors_list：[1,2]的话，你会发现还是会报错，.is_valid()这里报错了，为什么呢，因为，序列化组件校验的时候，在model表中找不到一个叫做authors_list的字段，所以还是报错，所以，在这里有个办法就是将这个序列化组件中的这个字段改个名字，不能和authors名字一样，并且使用默认配置(也就是read_only=true)
    # def get_authors_list(self,obj):
    def get_authors_list(self,obj):
        author_list_values = []
        author_list = obj.authors.all()
        for i in author_list:
            author_dict = {}
            author_dict['id'] = i.pk
            author_dict['name'] = i.name
            author_list_values.append(author_dict)
        return author_list_values
    # publish = serializers.CharField(max_length=32, source='publish.name',read_only=True) #如果这个字段名字和数据表中外键字段名称相同，并且设置了read_only=True属性，那么当用户提交数据到后端保存的时候，就会报错NOT NULL constraint failed: app01_book.publish_id，1.要么你将这个名字改成别的名字，2.要么去数据库表中将这个字段设置一个null=True,但是第二种方式肯定是不太好的，记住，当你获取数据时，使用这个序列化组件，即便是这个字段的名字和数据表中字段名字相同，也是没有问题的，只有在用户提交数据保存的时候才会有问题，所以最好的解决方式就是加read_only属性，并且改一下字段名字，不要和数据表中这个字段的名字相同
    publish_name = serializers.CharField(max_length=32, source='publish.name',read_only=True)

View of two components (mix Mixin class)

　　According to our view of the above sequence of components, and then write, above us only say a few interface operations Book a table, but we are not there other tables do ah, if we do the above four tables are some of the sequences the operation of the interface, we are not in the following way to write ah

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):

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


    def post(self,request,*args,**kwargs):
        print(request.data)
        bs=BookSerializers(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 BookDetailViewSet(APIView):

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

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

　　Well, this way, we look at an object-oriented usage of multiple inheritance:

class Animal:
    def __init__(self,name,age):
        self.name = name
        self.age = age
    def eat(self):
        print('吃')
    def drink(self):
        print('喝')
    #eat和drink才是动物共有的，下面三个不是共有的，所以直接这么些就不合适了,所以看下面的写法，单独写一些类，其他一部分动物有的，放到一个类里面，在多继承
    # def eatshit(self):
    #     print('吃s')
    # def zhiwang(self):
    #     print('织网')
    # def flying(self):
    #     print('飞')

class Eatshit:
    def eatshit(self):
        print('吃s')

class Zhiwang:
    def zhiwang(self):
        print('织网')

class Flying:
    def zhiwang(self):
        print('织网')

class Jumping:
    def zhiwang(self):
        print('跳')

class Dog(Animal,Eatshit):pass

class Spider(Animal,Zhiwang):pass

class Bird(Animal,Flying):pass

class Daishu(Animal,Flying,Jumping):pass

　　Well, based on this form of inheritance, we are not to be considered, and that we face several interfaces on the operation of each table, data processing logic we are almost ah, but you will find so many tables, I GET each table, PUT, DELETE, POST fact, almost all operations, changes can not happen again basically two places where we called two variables.

publish_list=Publish.objects.all()  #表所有的数据
bs=PublshSerializers(publish_list,many=True,context={'request': request})  #序列化组件

　　Mixin mixed class

　　　　Logical operation on data processing, drf help us a good package of several Mixin class, we play on the line, look at the code:

from django.shortcuts import render,HttpResponse,redirect
from django.views import View
from app01 import models

from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework import serializers

#将序列化组件都放到一个单独的文件里面，然后引入进来
from app01.serializer import BookSerializers,PublishSerializers
from rest_framework import generics

from rest_framework.mixins import ListModelMixin,CreateModelMixin,UpdateModelMixin,DestroyModelMixin,RetrieveModelMixin
# ListModelMixin 查看所有数据，对应着咱们上面的get查看所有数据的接口
# CreateModelMixin 添加数据的操作，封装了一个create操作，对应着上面的POST添加数据的几口
# UpdateModelMixin 更新
# DestroyModelMixin 销毁(删除)
# RetrieveModelMixin 获取单条数据
# 我们自己提炼出，说，每个表的操作基本都是上面的get、post、delete、put操作，所以我们想将这几个方法提炼出来，将来供其他类来继承使用，那么drf帮我们封装好了，就是这几个Minin类


class PublishView(ListModelMixin,CreateModelMixin,generics.GenericAPIView):
    '''
        GenericAPIView肯定继承了APIView，因为APIView里面的功能是我们必须的，而这个GenericAPIView是帮我们做衔接用的，把你的APIView的功能和我们的Minin类的功能衔接、调度起来的
    '''
    #继承完了之后，我们需要将我们前面各个表的序列化中提炼的两个不同的变量告诉咱的类，注意，下面的两个变量名就是他们俩，不能改，并且必须给
    queryset = models.Publish.objects.all()
    serializer_class = PublishSerializers
    def get(self,request):
        '''
        分发找到对应的请求方法，就是咱的get方法，而处理数据的逻辑是继承的那个ListModelMixin类里面的list方法做了，所以我们只需要return self.list(request方法就行了，处理数据的逻辑就不要我们自己再写了
        :param request:
        :return:
        '''

        return self.list(request) #list方法帮我们做了序列化

    #post方法添加一条数据，我们只需要执行一下CreateModelMixin类中的create方法就行了
    def post(self,request):
        return self.create(request)


class SPublishView(UpdateModelMixin,DestroyModelMixin,RetrieveModelMixin,generics.GenericAPIView):
　　#下面这两个变量和对应数据是必须给的
    queryset = models.Publish.objects.all()  
    serializer_class = PublishSerializers

    # def get(self,request,id):#id就不需要传了，因为人家要求在url中添加的命名分组的pk参数自动来做了
    def get(self,request, *args, **kwargs): #*args, **kwargs是为了接收url的那些参数的，咱们写的有个pk参数。
        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)

　　Class serialized components we put in a separate file, called serializer.py, reads as follows

from app01 import models
from rest_framework import serializers

class BookSerializers(serializers.ModelSerializer):
    class Meta:
        model=models.Book
        fields = "__all__"

class PublishSerializers(serializers.ModelSerializer):
    class Meta:
        model=models.Publish
        fields = "__all__"

　　urls.py reads as follows:

from django.conf.urls import url
from django.contrib import admin
from app01 import views
urlpatterns = [#publish表的接口
    url(r'^publishs/$', views.PublishView.as_view(),),
    # url(r'^publishs/(\d+)/', views.SPublishView.as_view(),), 
    #使用UpdateModelMixin，DestroyModelMixin，RetrieveModelMixin这类Mixin类的时候，人家要求必须有个命名分组参数，名字叫做pk，名字可以改，但是先这样用昂
    url(r'^publishs/(?P<pk>\d+)/', views.SPublishView.as_view(),),

]

　　After playing these classes drf mixing, you will find that the same logic for processing data portion is omitted, to simplify the code a lot.

　　But you see, we just wrote above publish a list of operations, we have some other table it, their action is not also GET, POST, DELETE, PUT and other operations ah, so you do not have a place to think about optimization

####################Author表操作##########################
ListCreateAPIView类就帮我们封装了get和create方法
class AuthorView(generics.ListCreateAPIView):

    queryset = models.Author.objects.all()
    serializer_class = AuthorSerializers

#RetrieveUpdateDestroyAPIView这个类封装了put、get、patch、delete方法
class SAuthorView(generics.RetrieveUpdateDestroyAPIView):

    queryset = models.Author.objects.all()
    serializer_class = AuthorSerializers

　　Then you look at, as well as to optimize the place, the above two categories stuff inside is the same, ah, can not go heavy, of course, can, get a class, look at the wording

#####################再次封装的Author表操作##########################
from rest_framework.viewsets import ModelViewSet #继承这个模块
class AuthorView(ModelViewSet):
    queryset = models.Author.objects.all()
    serializer_class = AuthorSerializers

　　But the url must be changed, look at the wording of the url:

#这两个url用的都是上面的一个类url(r'^authors/$', views.AuthorView.as_view({"get":"list","post":"create"}),),
url(r'^authors/(?P<pk>\d+)/', views.AuthorView.as_view({
                'get': 'retrieve',
                'put': 'update',
                'patch': 'partial_update',
                'delete': 'destroy'
            }),),

　　Then restart your own program, as measured by the postman look, certainly can.

　　Well, how to play with this thing? Are interested, you can go look at the source ~~~

　　In fact, the source of the most critical point is this:

        def view(request, *args, **kwargs):
            self = cls(**initkwargs)
            # We also store the mapping of request methods to actions,
            # so that we can later set the action attribute.
            # eg. `self.action = 'list'` on an incoming GET request.
            self.action_map = actions

            # Bind methods to actions
            # This is the bit that's different to a standard view　　　　　　　#就下面这三句，非常巧妙
            for method, action in actions.items(): {'get':'list',}
                handler = getattr(self, action) #肯定能找到对应的方法list handler = self.list
                setattr(self, method, handler)  #self.get = self.list　　　　　　  后面再执行dispatch方法之后，那个handler = getattr(self,request.method.lower()) #找到的是list方法去执行的，因为self.get等于self.list了,然后执行list方法，返回对应的内容

　　We do all of the above data interface, but there are logical interfaces, such as landing, as this data interface directly write a class Login (APIView): pass this on to carry out his line, packaging simpler and more complex internal logic, customized to the more complex, so on a different logic, we own a single write.

注意1：
#通过self在继承类之间调用变量，现在是我们通过Dog类继承的Animal类中调用了Running类中的变量,也就是说如果你在某个类中找不到对应的属性，有可能在其他类里面放着了
class Animal:
    x=10
    def foo(self):
        print(self.x)

class Running:
    x = 20

#在Animal类中加一个类变量x，然后把下面继承的两个类的顺序发生一下变化，你看看会出现什么情况
class Dog(Animal,Running):
# class Dog(Running, Animal):
    pass

d = Dog() 
d.foo()  #20

注意2：给函数传一个字典数据进去，到底这个字典给了下面哪个形参。
def f1(action,**kwargs):
    print(action) 
    print(kwargs) 

f1({'name':'chao'}) #结果：{'name': 'chao'} {}
# f1(x=1) #报错：TypeError: f1() missing 1 required positional argument: 'action'
f1(1,x=1) #结果： 1  {'x': 1}

　　Then you curious about it, want to see put \ operation get \ delete, the inside of the pk url named route, in the end why called pk, and, through its own internally how to find the update before pk value corresponding to the the original model object ah?