表断关系，和modlesserializers序列化，反序列化

课程准备

配置：settings.py

INSTALLED_APPS = [
    # ...
    'rest_framework',
]
​
DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'dg_proj',
        'USER': 'root',
        'PASSWORD': '123',
    }
}
"""
任何__init__文件
import pymysql
pymysql.install_as_MySQLdb()
"""
​
LANGUAGE_CODE = 'zh-hans'
TIME_ZONE = 'Asia/Shanghai'
USE_I18N = True
USE_L10N = True
USE_TZ = False
​
MEDIA_URL = '/media/'
MEDIA_ROOT = os.path.join(BASE_DIR, 'media')

路由

# 主
from django.conf.urls import url, include
from django.contrib import admin
from django.views.static import serve
from django.conf import settings
urlpatterns = [
    url(r'^admin/', admin.site.urls),
    url(r'^api/', include('api.urls')),
    url(r'^media/(?P<path>.*)', serve, {'document_root': settings.MEDIA_ROOT}),
]
​
# 子
from django.conf.urls import url
from . import views
urlpatterns = [
     
]

多表设计

"""
Book表：name、price、img、authors、publish、is_delete、create_time
​
Publish表：name、address、is_delete、create_time
     
Author表：name、age、is_delete、create_time
​
AuthorDetail表：mobile, author、is_delete、create_time
     
BaseModel基表
    is_delete、create_time
上面四表继承基表，可以继承两个字段
"""

基表

class BaseModel(models.Model):
    is_delete = models.BooleanField(default=False)
    create_time = models.DateTimeField(auto_now_add=True)
​
    # 设置 abstract = True 来声明基表，作为基表的Model不能在数据库中形成对应的表
    class Meta:
        abstract = True

断关联多表关系

知识点（重点）

"""
1、外键位置：
    一对多 - 外键放多的一方
    一对一 - 从逻辑正反向考虑，如作者表与作者详情表，作者删除级联删除详情，详情删除作者依旧存在，所以建议外键在详情表中
    多对多 - 外键在关系表中
     
2、ORM正向方向连表查找：
    正向：通过外键字段 eg: author_detial_obj.author 
    反向：通过related_name的值 eg：author_obj.detail
    注：依赖代码见下方
     
3、连表操作关系：
    1）作者删除，详情级联 - on_delete=models.CASCADE
    2）作者删除，详情置空 - null=True, on_delete=models.SET_NULL
    3）作者删除，详情重置 - default=0, on_delete=models.SET_DEFAULT
    4）作者删除，详情不动 - on_delete=models.DO_NOTHING
    注：拿作者与作者详情表举例
     
4、外键关联字段的参数 - 如何实现 断关联、目前表间操作关系、方向查询字段
    i）作者详情表中的
    author = models.OneToOneField(
        to='Author',
        related_name='detail',
        db_constraint=False,
        on_delete=models.CASCADE
    )
     
    ii）图书表中的
    publish = models.ForeignKey(
        to='Publish',
        related_name='books',
        db_constraint=False,
        on_delete=models.DO_NOTHING,
    )
    authors = models.ManyToManyField(
        to='Author'
        related_name='books',
        db_constraint=False,
    )
    注：ManyToManyField不能设置on_delete，OneToOneField、ForeignKey必须设置on_delete（django1.x系统默认级联，但是django2.x必须手动明确）
"""

model类

from django.db import models
​
# 图书管理系统：Book、Author、AuthorDetail、Publish
"""
Book表: name、price、img、authors、publish、is_delete、create_time
Publish表: name、address、is_delete、create_time
Author表: name、age、is_delete、create_time
AuthorDetail表: mobile, author、is_delete、create_time
"""
​
# 1) 基表
class BaseModel(models.Model):
    is_delete = models.BooleanField(default=False)
    create_time = models.DateTimeField(auto_now_add=True)
​
    # 作为基表的Model不能在数据库中形成对应的表，设置 abstract = True
    class Meta:
        abstract = True
​
​
class Book(BaseModel):
    """name、price、img、authors、publish、is_delete、create_time"""
    name = models.CharField(max_length=64)
    price = models.DecimalField(max_digits=5, decimal_places=2)
    img = models.ImageField(upload_to='img', default='img/default.jpg')
    publish = models.ForeignKey(
        to='Publish',
        db_constraint=False,  # 断关联
        related_name='books',  # 反向查询字段：publish_obj.books 就能访问所有出版的书
        on_delete=models.DO_NOTHING,  # 设置连表操作关系
    )
    authors = models.ManyToManyField(
        to='Author',
        db_constraint=False,
        related_name='books'
    )
​
    # 序列化插拔式属性 - 完成自定义字段名完成连表查询
    @property
    def publish_name(self):
        return self.publish.name
​
    @property
    def author_list(self):
        return self.authors.values('name', 'age', 'detail__mobile').all()
​
    class Meta:
        db_table = 'book'
        verbose_name = '书籍'
        verbose_name_plural = verbose_name
    def __str__(self):
        return self.name
​
class Publish(BaseModel):
    """name、address、is_delete、create_time"""
    name = models.CharField(max_length=64)
    address = models.CharField(max_length=64)
​
    class Meta:
        db_table = 'publish'
        verbose_name = '出版社'
        verbose_name_plural = verbose_name
    def __str__(self):
        return self.name
​
class Author(BaseModel):
    """name、age、is_delete、create_time"""
    name = models.CharField(max_length=64)
    age = models.IntegerField()
​
    class Meta:
        db_table = 'author'
        verbose_name = '作者'
        verbose_name_plural = verbose_name
    def __str__(self):
        return self.name
​
class AuthorDetail(BaseModel):
    """mobile, author、is_delete、create_time"""
    mobile = models.CharField(max_length=11)
    author = models.OneToOneField(
        to='Author',
        db_constraint=False,
        related_name='detail',
        on_delete=models.CASCADE,
    )
​
    class Meta:
        db_table = 'author_detail'
        verbose_name = '作者详情'
        verbose_name_plural = verbose_name
    def __str__(self):
        return '%s的详情' % self.author.name

序列化

序列化层：api/serializers.py

from rest_framework.serializers import ModelSerializer, SerializerMethodField
from rest_framework.exceptions import ValidationError
from . import models
​
# 可以单独作为Publish接口的序列化类，也可以作为Book序列化外键publish辅助的序列化组件
class PublishModelSerializer(ModelSerializer):
    class Meta:
        model = models.Publish
        fields = ('name', 'address')
​
class BookModelSerializer(ModelSerializer):
    # 了解: 该方式设置的序列化字段，必须在fields中声明
    # publish_address = SerializerMethodField()
    # def get_publish_address(self, obj):
    #     return obj.publish.address
​
    # 自定义连表深度 - 子序列化方式 - 该方式不能参与反序列化，使用在序列化反序列化共存时，不能书写
    publish = PublishModelSerializer()
​
    class Meta:
        # 序列化类关联的model类
        model = models.Book
        # 参与序列化的字段
        fields = ('name', 'price', 'img', 'author_list', 'publish')
​
        # 了解知识点
        # 所有字段
        # fields = '__all__'
        # 与fields不共存，exclude排除哪些字段
        # exclude = ('id', 'is_delete', 'create_time')
        # 自动连表深度
        # depth = 1

视图层：api/views.py

class Book(APIView):
    def get(self, request, *args, **kwargs):
        pk = kwargs.get('pk')
        if pk:
            try:
                book_obj = models.Book.objects.get(pk=pk, is_delete=False)
                book_data = serializers.BookModelSerializer(book_obj).data
            except:
                return Response({
                    'status': 1,
                    'msg': '书籍不存在'
                })
        else:
            book_query = models.Book.objects.filter(is_delete=False).all()
            book_data = serializers.BookModelSerializer(book_query, many=True).data
        return Response({
            'status': 0,
            'msg': 'ok',
            'results': book_data
        })　

路由层：api/urls.py

urlpatterns = [
    url(r'^books/$', views.Book.as_view()),
    url(r'^books/(?P<pk>.*)/$', views.Book.as_view()),
]

反序列化

序列化层：api/serializers.py

class BookModelDeserializer(ModelSerializer):
    class Meta:
        model = models.Book
        fields = ('name', 'price', 'publish', 'authors')
        # extra_kwargs 用来完成反序列化字段的 系统校验规则
        extra_kwargs = {
            'name': {
                'required': True,
                'min_length': 1,
                'error_messages': {
                    'required': '必填项',
                    'min_length': '太短',
                }
            }
        }
     
    # 局部钩子
    def validate_name(self, value):
        # 书名不能包含 g 字符
        if 'g' in value.lower():
            raise ValidationError('该g书不能出版')
        return value
    # 全局钩子
    def validate(self, attrs):
        publish = attrs.get('publish')
        name = attrs.get('name')
        if models.Book.objects.filter(name=name, publish=publish):
            raise ValidationError({'book': '该书已存在'})
        return attrs
​
    # ModelSerializer类已经帮我们实现了 create 与 update 方法

视图层：api/views.py

class Book(APIView):
    def post(self, request, *args, **kwargs):
        request_data = request.data
        book_ser = serializers.BookModelDeserializer(data=request_data)
        # raise_exception=True：当校验失败，马上终止当前视图方法，抛异常返回给前台
        book_ser.is_valid(raise_exception=True)
        book_obj = book_ser.save()
        return Response({
            'status': 0,
            'msg': 'ok',
            'results': serializers.BookModelSerializer(book_obj).data
        })

路由层：api/urls.py

urlpatterns = [
    url(r'^books/$', views.Book.as_view()),
    url(r'^books/(?P<pk>.*)/$', views.Book.as_view()),
]

序列化与反序列化整合（重点）

序列化层：api/serializers.py

"""
1) fields中设置所有序列化与反序列化字段
2) extra_kwargs划分只序列化或只反序列化字段
    write_only：只反序列化
    read_only：只序列化
    自定义字段默认只序列化(read_only)
3) 设置反序列化所需的 系统、局部钩子、全局钩子 等校验规则
"""
class V2BookModelSerializer(ModelSerializer):
    class Meta:
        model = models.Book
        fields = ('name', 'price', 'img', 'author_list', 'publish_name', 'publish', 'authors')
        extra_kwargs = {
            'name': {
                'required': True,
                'min_length': 1,
                'error_messages': {
                    'required': '必填项',
                    'min_length': '太短',
                }
            },
            'publish': {
                'write_only': True
            },
            'authors': {
                'write_only': True
            },
            'img': {
                'read_only': True,
            },
            'author_list': {
                'read_only': True,
            },
            'publish_name': {
                'read_only': True,
            }
        }
​
    def validate_name(self, value):
        # 书名不能包含 g 字符
        if 'g' in value.lower():
            raise ValidationError('该g书不能出版')
        return value
​
    def validate(self, attrs):
        publish = attrs.get('publish')
        name = attrs.get('name')
        if models.Book.objects.filter(name=name, publish=publish):
            raise ValidationError({'book': '该书已存在'})

 　　　　return attrs

视图层：api/views.py

class V2Book(APIView):
    # 单查：有pk
    # 群查：无pk
    def get(self, request, *args, **kwargs):
        pk = kwargs.get('pk')
        if pk:
            try:
                book_obj = models.Book.objects.get(pk=pk, is_delete=False)
                book_data = serializers.V2BookModelSerializer(book_obj).data
            except:
                return Response({
                    'status': 1,
                    'msg': '书籍不存在'
                })
        else:
            book_query = models.Book.objects.filter(is_delete=False).all()
            book_data = serializers.V2BookModelSerializer(book_query, many=True).data
        return Response({
            'status': 0,
            'msg': 'ok',
            'results': book_data
        })
​
    # 单增：传的数据是与model对应的字典
    # 群增：传的数据是 装多个 model对应字典 的列表
    def post(self, request, *args, **kwargs):
        request_data = request.data
        if isinstance(request_data, dict):
            many = False
        elif isinstance(request_data, list):
            many = True
        else:
            return Response({
                'status': 1,
                'msg': '数据有误',
            })
        book_ser = serializers.V2BookModelSerializer(data=request_data, many=many)
        # 当校验失败，马上终止当前视图方法，抛异常返回给前台
        book_ser.is_valid(raise_exception=True)
        book_result = book_ser.save()
        return Response({
            'status': 0,
            'msg': 'ok',
            'results': serializers.V2BookModelSerializer(book_result, many=many).data
        })
​
    # 单删：有pk
    # 群删：有pks   |  {"pks": [1, 2, 3]}
    def delete(self, request, *args, **kwargs):
        pk = kwargs.get('pk')
        if pk:
            pks = [pk]
        else:
            pks = request.data.get('pks')
        if models.Book.objects.filter(pk__in=pks, is_delete=False).update(is_delete=True):
            return Response({
                'status': 0,
                'msg': '删除成功',
            })
        return Response({
            'status': 1,
            'msg': '删除失败',
        })　

路由层：api/urls.py

urlpatterns = [
    url(r'^v2/books/$', views.V2Book.as_view()),
    url(r'^v2/books/(?P<pk>.*)/$', views.V2Book.as_view()),
]

整体单改

路由层、模型层、序列化层不需要做修改，只需要处理视图层：views.py

"""
1) 单整体改，说明前台要提供修改的数据，那么数据就需要校验，校验的数据应该在实例化“序列化类对象”时，赋值给data
2）修改，就必须明确被修改的模型类对象，并在实例化“序列化类对象”时，赋值给instance
3）整体修改，所有校验规则有required=True的字段，都必须提供，因为在实例化“序列化类对象”时，参数partial默认为False
​
​
注：如果partial值设置为True，就是可以局部改
1）单整体修改，一般用put请求：
V2BookModelSerializer(
    instance=要被更新的对象, 
    data=用来更新的数据,
    partial=默认False，必须的字段全部参与校验
)
2）单局部修改，一般用patch请求：
V2BookModelSerializer(
    instance=要被更新的对象, 
    data=用来更新的数据,
    partial=设置True，必须的字段都变为选填字段
)
    注：partial设置True的本质就是使字段 required=True 校验规则失效
"""

class V2Book(APIView):
    # 单整体改: 对 v2/books/(pk)/ 传的数据是与model对应的字典{name|price|publish|authors}
    def put(self, request, *args, **kwargs):
        request_data = request.data
        pk = kwargs.get('pk')
        old_book_obj = models.Book.objects.filter(pk=pk).first()
        # 目的：将众多数据的校验交给序列化类来处理 - 让序列化类扮演反序列化角色，校验成功后，序列化类来帮你入库
        book_ser = serializers.V2BookModelSerializer(instance=old_book_obj, data=request_data, partial=False)
        book_ser.is_valid(raise_exception=True)
        # 校验通过，完成数据的更新：要更新的目标，用来更新的新数据
        book_obj = book_ser.save()
​
        return Response({
            'status': 0,
            'msg': 'ok',
            'results': serializers.V2BookModelSerializer(book_obj).data
        })

单与整体局部修改

序列化层：serializers.py

# 重点：ListSerializer与ModelSerializer建立关联的是：
# ModelSerializer的Meta类的 - list_serializer_class
class V2BookListSerializer(ListSerializer):
    def update(self, instance, validated_data):
        # print(instance)  # 要更新的对象们
        # print(validated_data)  # 更新的对象对应的数据们
        # print(self.child)  # 服务的模型序列化类 - V2BookModelSerializer
        for index, obj in enumerate(instance):
            self.child.update(obj, validated_data[index])
        return instance
     
# 原模型序列化类变化
class V2BookModelSerializer(ModelSerializer):
    class Meta:
        # ...
        # 群改，需要设置 自定义ListSerializer，重写群改的 update 方法
        list_serializer_class = V2BookListSerializer
    # ...

视图层：views.py

class V2Book(APIView):
    # 单局部改：对 v2/books/(pk)/ 传的数据，数据字段key都是选填
    # 群局部改：对 v2/books/ 
    # 请求数据 - [{pk:1, name:123}, {pk:3, price:7}, {pk:7, publish:2}]
    def patch(self, request, *args, **kwargs):
        request_data = request.data
        pk = kwargs.get('pk')
​
        # 将单改，群改的数据都格式化成 pks=[要需要的对象主键标识] | request_data=[每个要修改的对象对应的修改数据]
        if pk and isinstance(request_data, dict):  # 单改
            pks = [pk, ]
            request_data = [request_data, ]
        elif not pk and isinstance(request_data, list): # 群改
            pks = []
            for dic in request_data:  # 遍历前台数据[{pk:1, name:123}, {pk:3, price:7}, {pk:7, publish:2}]，拿一个个字典
                pk = dic.pop('pk', None)
                if pk:
                    pks.append(pk)
                else:
                    return Response({
                        'status': 1,
                        'msg': '数据有误',
                    })
        else:
            return Response({
                'status': 1,
                'msg': '数据有误',
            })
​
        # pks与request_data数据筛选，
        # 1）将pks中的没有对应数据的pk与数据已删除的pk移除，request_data对应索引位上的数据也移除
        # 2）将合理的pks转换为 objs
       objs = []
        new_request_data = []
        for index,pk in enumerate(pks):
            book_obj = models.Book.objects.filter(pk=pk).first()
            if book_obj:
                objs.append(book_obj)
                new_request_data.append(request_data[index])
                 
​
        book_ser = serializers.V2BookModelSerializer(instance=objs, data=new_request_data, partial=True, many=True)
        book_ser.is_valid(raise_exception=True)
        book_objs = book_ser.save()
​
        return Response({
            'status': 0,
            'msg': 'ok',
            'results': serializers.V2BookModelSerializer(book_objs, many=True).data
        })

视图类传递参数给序列化类

# 1）在视图类中实例化序列化对象时，可以设置context内容
# 2）在序列化类中的局部钩子、全局钩子、create、update方法中，都可以用self.context访问视图类传递过来的内容
​
​
# 需求：
# 1) 在视图类中，可以通过request得到登陆用户request.user
# 2) 在序列化类中，要完成数据库数据的校验与入库操作，可能会需要知道当前的登陆用户，但序列化类无法访问request
# 3) 在视图类中实例化序列化对象时，将request对象传递进去

视图层：views.py

class Book(APIView):
    def post(self, request, *args, **kwargs):
        book_ser = serializers.BookModelSerializer(data=request_data,context={'request':request})
        book_ser.is_valid(raise_exception=True)
        book_result = book_ser.save()
        return Response({
            'status': 0,
            'msg': 'ok',
            'results': serializers.BookModelSerializer(book_result).data
        })　

序列化层：serializers.py

class BookModelSerializer(ModelSerializer):
    class Meta:
        model = models.Book
        fields = ('name', 'price')
    def validate_name(self, value):
        print(self.context.get('request').method)
        return value

二次封装Response类

"""
Response({
    'status': 0,
    'msg': 'ok',
    'results': [],
    'token': ''  # 有这样的额外的key-value数据结果
},status=http_status,headers=headers,exception=True|False)
​
APIResponse() => Response({'status': 0,'msg': 'ok'})
"""
from rest_framework.response import Response
​
class APIResponse(Response):
    def __init__(self, data_status=0, data_msg='ok', results=None, http_status=None, headers=None, exception=False, **kwargs):
        # data的初始状态：状态码与状态信息
        data = {
            'status': data_status,
            'msg': data_msg,
        }
        # data的响应数据体
        # results可能是False、0等数据，这些数据某些情况下也会作为合法数据返回
        if results is not None:
            data['results'] = results
        # data响应的其他内容
        # if kwargs is not None:
        #     for k, v in kwargs.items():
        #         setattr(data, k, v)
        data.update(kwargs)
​
        super().__init__(data=data, status=http_status, headers=headers, exception=exception)