ModelSerializer 序列化和反序列化，及序列化整合，单删/增，群删/增（delete请求）

ModelSerializer 序列化
序列化准备

- 模型层：models.py
from django.db import models

# 1.基表模型类的封装（建立公有字段）
class BaseModel(models.Model):
    is_delete = models.BooleanField(default=False)
    create_time = models.DateTimeField(auto_now_add=True)  # 创建的时候更新时间

    # 作为基表的model一定要加上，迁移命令之后不会在数据库中生成表
    class Meta:
        abstract = True


class Book(BaseModel):
    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,
                                related_name="books",
                                on_delete=models.DO_NOTHING
                                )
    authors = models.ManyToManyField(to="Author",
                                     db_constraint=False,
                                     related_name='books',
                                     )

    def fn(self):
        return 'fn fn fn '

    # 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 = '书籍表'
        verbose_name_plural = verbose_name

    def __str__(self):
        return self.name


class Publish(BaseModel):
    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 = models.CharField(max_length=64)
    age = models.IntegerField()

    class Meta:
        db_table = 'author'
        verbose_name = '作者表'
        verbose_name_plural = verbose_name

    def __str__(self):
        return self.name


class AuthorDetail(BaseModel):
    mobile = models.CharField(max_length=11)
    author = models.OneToOneField(to="Author",
                                  db_constraint=False,
                                  on_delete=models.CASCADE,
                                  related_name='detail'
                                  )
    db_constraint=False断关联
    # 1.作者删除，详情也跟着删除  - 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.DD_NOTHING
    class Meta:
        db_table = 'authorDetail'
        verbose_name = '作者详情'
        verbose_name_plural = verbose_name

db_constraint=False断关联

"""
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）
"""

- 后台管理层：admin.py

```注册
from django.contrib import admin
from . import models

admin.site.register(models.User)  # 只要需要后台操作都要注册

 - 配置层：settings.py

# 注册rest_framework
INSTALLED_APPS = [
    # ...
    'rest_framework',
]

# media资源
MEDIA_URL = '/media/'  # 后期高级序列化类与视图类，会使用该配置
MEDIA_ROOT = os.path.join(BASE_DIR, 'media')  # media资源路径

# 国际化配置
LANGUAGE_CODE = 'zh-hans'
TIME_ZONE = 'Asia/Shanghai'
USE_I18N = True
USE_L10N = True
USE_TZ = False

#### 序列化使用
##在api中建立一个serializers.py文件夹


- 序列化层：api/serializers.py

from rest_framework.serializers import ModelSerializer, SerializerMethodField

from . import models

class PublishModelSerializer(ModelSerializer):
    class Meta:
        model = models.Publish
        fields = '__all__'

# 序列化发送数据给前端
class BookModelSerializer(ModelSerializer):
    # 了解，这样的字段规定了必须查找在fileds中申明，否则报错
    # 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,定义之后必须在fields注册，否则报错
    publish = PublishModelSerializer()

    class Meta:
        # 序列化关联的model类
        model = models.Book

        # 参与序列化的字段
        fields = ('name', 'price', 'img', 'publish_name', 'author_list','publish')
        # fields ='__all__'  # 显示所有字段

        # exclude = ("id", "is_delete", "create_time")  # 除开哪些字段
        # 自动连表深度
        # depth =1

# 视图层（views）

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": '访问成功',
            "results": book_data
        })

## 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 “required：True 必须校验
        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()),
]
```