django-ContentType的简单使用

ContentType

　　一般我们有多张表同时外键关联同一张表的时候，可以考虑使用ContentType

models.py

 from django.db import models
 from django.contrib.contenttypes.models import ContentType # django自己生成的表，里面存储着每一个app和它下面的表关系
 from django.contrib.contenttypes.fields import GenericForeignKey, GenericRelation

 class PythonBasic(models.Model):
     course_name = models.CharField(max_length=32)
     coupons = GenericRelation(to='Coupon') ##相当于foreignkey

 class Oop(models.Model):
     course_name = models.CharField(max_length=32)
     coupons = GenericRelation(to='Coupon') ##相当于foreignkey

 class Coupon(models.Model):
     coupon_name = models.CharField(max_length=32)
     content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE) ##
     object_id = models.PositiveIntegerField() ##

     content_object = GenericForeignKey("content_type", "object_id") ## 在表中不会真的生成这个字段，但是对应关系是靠它实现的

views.py

 class ContentTypeView(View):

     def get(self, request):
         # 获取表名
         # pb = ContentType.objects.filter(app_label='app01', model='pythonbasic').first()
         # print(pb.model_class()) # <class 'app01.models.PythonBasic'>
         # print(pb.model_class().objects.all()) # <QuerySet [<PythonBasic: PythonBasic object (1)>, <PythonBasic: PythonBasic object (2)>, <PythonBasic: PythonBasic object (3)>]>

         # obj = PythonBasic.objects.get(id=3)
         obj = Oop.objects.get(id=2)
         # Coupon.objects.create(coupon_name="Python基础通关", content_object=obj)
         print(obj.coupons.all())

         return HttpResponse('ok')