drf 05

1、完成汽车系统表模型的建立（表关系自己设计）
	汽车表、汽车商家表、赞助商表、赞助商详情表

2、完成汽车系统的接口编写
	汽车表：八大接口(不需要写put方法)
	汽车商家表：八大接口(不需要写put方法

"""
related_name反查参数，设置后可以在被关联表中通过该字段反查外键所在表
on_delete：当该表中的某条数据删除后，关联外键的操作
CASCADE:这就是默认的选项，级联删除，你无需显性指定它。
PROTECT: 保护模式，如果采用该选项，删除的时候，会抛出ProtectedError错误。
SET_NULL: 置空模式，删除的时候，外键字段被设置为空，前提就是blank=True, null=True,定义该字段的时候，允许为空。
SET_DEFAULT: 置默认值，删除的时候，外键字段设置为默认值，所以定义外键的时候注意加上一个默认值。
SET(): 自定义一个值，该值当然只能是对应的实体了
如果使用两个表之间存在关联,首先db_constraint=False 把关联切断,但保留链表查询的功能,其次要设置null=True, 
blank=True,注意on_delete=models.SET_NULL 一定要置空,这样删了不会影响其他关联的表
db_table  第三张表的名字
db_constraint=False,这个就是保留跨表查询的便利(双下划线跨表查询```),但是不用约束字段了,一半公司都用false,
这样就省的报错,因为没有了约束(Field字段对象,既约束,又建立表与表之间的关系)
"""

# api>urls.py
from . import views
from django.conf.urls import url

urlpatterns = [
    url(r'^v1/cars/$',views.CarAPIView.as_view()),
    url(r'^v1/cars/(?P<pk>d+)/$',views.CarAPIView.as_view())
]

# ============================================================================================= 
# views.py
from rest_framework.views import APIView
from rest_framework.response import Response
from .response import APIResponse
from . import models, serializers
class CarAPIView(APIView):
    # 群查
    def get(self, request, *args, **kwargs):
        car_query = models.Car.objects.filter(is_delete=False).all()
        car_ser = serializers.CarModelSerializer(instance=car_query, many=True)
        return APIResponse(results=car_ser.data)
# =============================================================================================  
# models.py
# 基表
class BaseModel(models.Model):
    is_delete = models.BooleanField(default=False)
    create_time = models.DateTimeField(auto_now_add=True)

    class Meta:
        abstract=True

# 汽车表
class Car(BaseModel):
    name = models.CharField(max_length=64,verbose_name = '车名')
    price = models.DecimalField(max_digits=10, decimal_places=2,verbose_name = '价格')
    brand = models.ForeignKey(to='Brand',db_constraint=False,null=True,on_delete=models.SET_NULL)
    sponsors = models.ManyToManyField(to='Sponsor',db_constraint=False)

    @property
    def brand_name(self):
        return self.brand.name

    @property
    def sponsor_list(self):
        sponsor_list_temp = []
        for sponsor in self.sponsors.all():
            sponsor_dic = {
                'name': sponsor.name
            }
            try:
                sponsor_dic['phone'] = sponsor.sponsordetail.phone
            except:
                sponsor_dic['phone'] = '未知'
            sponsor_list_temp.append(sponsor_dic)
        return sponsor_list_temp
    class Meta:
        verbose_name_plural='汽车'
    def __str__(self):
        return self.name
# 汽车商家表
class Brand(BaseModel):
    name = models.CharField(max_length=32)

    class Meta:
        verbose_name_plural='汽车品牌'

    def __str__(self):
        return self.name
# 赞助商表
class Sponsor(BaseModel):
    name = models.CharField(max_length=64)

    class Meta:
        verbose_name_plural='赞助商'

    def __str__(self):
        return self.name
# 赞助详情表
class SponsorDetail(BaseModel):
    phone = models.CharField(max_length=11)
    sponsor = models.OneToOneField(to=Sponsor,db_constraint=False,on_delete=models.CASCADE)

    class Meta:
        verbose_name_plural='赞助商详情'

    def __str__(self):
        try:  # 连表可能会出现问题，所以要异常处理
            return self.sponsor.name + '的详情'
        except:
            return super().__str__()
 
# ============================================================================================= 
# serializers.py
from rest_framework import serializers
from . import models

class CarModelSerializer(serializers.ModelSerializer):
    class Meta:
        model=models.Car
        fields = ('name','price','brand_name','sponsor_list','brand','sponsors')
        extra_kwargs = {
            'brand': {
                'required': True,
                'write_only': True
            },
            'sponsors': {
                'required': True,
                'write_only': True
            },
        }
        
# ============================================================================================= 
# response.py
from rest_framework.response import Response
class APIResponse(Response):
    def __init__(self, status=0, msg='ok', results=None, http_status=None,
                 headers=None, exception=False, content_type=None, **kwargs):
        # 将status、msg、results、kwargs格式化成data
        data = {
            'status': status,
            'msg': msg,
        }
        # results只要不为空都是数据：False、0、'' 都是数据 => 条件不能写if results
        if results is not None:
            data['results'] = results
        # 将kwargs中额外的k-v数据添加到data中
        data.update(**kwargs)

        super().__init__(data=data, status=http_status, headers=headers, exception=exception, content_type=content_type)