自学教程：Django ContentType组件详解

from django.db import modelsclass Appliance(models.Model):    """    家用电器表    id name    1   冰箱    2   电视    3   洗衣机    """    name = models.CharField(max_length=64)class Food(models.Model):    """    食物表    id name    1  面包    2  牛奶    """    name = models.CharField(max_length=32)class Fruit(models.Model):    """    水果表    id  name    1   苹果    2   香蕉    """    name = models.CharField(max_length=32)class Coupon(models.Model):    """    优惠券表    id  name    appliance_id    food_id     fruit_id    1   通用优惠券   null            null        null    2   冰箱折扣券   1               null        null    3   电视折扣券   2               null        null    4   苹果满减卷   null            null        1    """    name = models.CharField(max_length=32)    appliance = models.ForeignKey(to="Appliance", null=True, blank=True)    food = models.ForeignKey(to="Food", null=True, blank=True)    fruit = models.ForeignKey(to="Fruit", null=True, blank=True)

#!/usr/bin/env python3# -*- coding: utf-8 -*-from django.db import modelsfrom django.contrib.contenttypes.models import ContentTypefrom django.contrib.contenttypes.fields import GenericForeignKey, GenericRelationclass Food(models.Model):    """    id      title    1       面包    2       牛奶    """    title = models.CharField(max_length=32)    # 不会生成coupons字段,只用于反向查询    coupons = GenericRelation(to="Coupon")class Fruit(models.Model):    """    id      title    1       苹果    2       香蕉    """    title = models.CharField(max_length=32)class Coupon(models.Model):    title = models.CharField(max_length=32)    # 第一步:在 model中定义ForeignKey字段,并关联到ContentType表    content_type = models.ForeignKey(to=ContentType, on_delete=None)    # 第二步:定义IntegerField字段,用来存储关联表中的主键    object_id = models.IntegerField()    # 第三步 不会生成字段传入上面两个字段的名字    content_object = GenericForeignKey("content_type", "object_id")

class DemoView(APIView):    def get(self, request):        # 1.通过ContentType表找表模型        content = ContentType.objects.filter(app_label="app1", model="food").first()        # 获得表model对象 相当于models.app1        model_class = content.model_class()        ret = model_class.objects.all()        print(ret)        # 给面包创建一个优惠券        food_obj = Food.objects.filter(id=1).first()        Coupon.objects.create(title="面包九五折", content_type_id=8, object_id=1)        Coupon.objects.create(title="双十一面包九折促销", content_object=food_obj)        # 正向查询:根据优惠信息查询优惠对象        coupon_obj = Coupon.objects.filter(id=1).first()        content_obj = coupon_obj.content_object        print(content_obj.title)        # 反向查询:查询面包都有哪些优惠券        coupons = food_obj.coupons.all()        print(coupons[0].title)        # 如果没定义反向查询        content = ContentType.objects.filter(app_label="app1", model="food").first()        result = Coupon.objects.filter(content_type=content, object_id=1).all()        print(result[0].name)        return Response("ContentType测试")