contenttypes
contenttypes组件的内部帮我们讲django的ORM中定义的所有表都自动手机起来，并保存至
后续开发中如果遇到 一张表 与 其他n张表进行关联，就可以基于contenttypes实现。
表定义
from django.db import models
from django.contrib.contenttypes.fields import GenericForeignKey, GenericRelation
from django.contrib.contenttypes.models import ContentType
class DegreeCourse(models.Model):
"""学位课程"""
name = models.CharField(max_length=128, unique=True)
# 用于GenericForeignKey反向查询，不会生成表字段
degree_price_policy = GenericRelation("PricePolicy")
class Course(models.Model):
"""课程"""
name = models.CharField(max_length=128, unique=True)
# 用于GenericForeignKey反向查询，不会生成表字段
price_policy = GenericRelation("PricePolicy")
class PricePolicy(models.Model):
"""价格与有课程效期表"""
content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE) # 关联course or degree_course
object_id = models.PositiveIntegerField()
# 方便设置值，不会生成表字段（直接设置为对象，自动生成 content_type和object_id）
content_object = GenericForeignKey('content_type', 'object_id')
price = models.IntegerField()
新建数据
def demo(request):
from app03 import models
models.Course.objects.create(name="APP逆向") # 1
models.Course.objects.create(name="django项目") # 2
models.Course.objects.create(name="小程序") # 3
models.DegreeCourse.objects.create(name="Python全栈") # 1
models.DegreeCourse.objects.create(name="爬虫") # 2
models.DegreeCourse.objects.create(name="Linux") # 3
models.PricePolicy.objects.create(
content_object=models.DegreeCourse.objects.get(name="Python全栈"),
priod="3个月",
price=100
)
models.PricePolicy.objects.create(
content_object=models.Course.objects.get(name="django项目"),
priod="6个月",
price=150
)
return HttpResponse("ok")
用于GenericForeignKey反向查询
obj = models.DegreeCourse.objects.filter(name="Python全栈").first()
print( obj.degree_price_policy.all() )
"""
<QuerySet [<PricePolicy: PricePolicy object (2)>]>
"""
查询
price_policy_queryset = models.PricePolicy.objects.all()
for obj in price_policy_queryset:
print(obj.content_object, obj.price)
"""
DegreeCourse object (1) 100
Course object (1) 200
"""
