Django的ContentType

如果一個表跟多個表都有外鍵關系, 那麼就用ContentType

1. model.py

   from django.db import models
   from django.contrib.contenttypes.models import ContentType
   # GenericRelation 用來反向查詢的
   from django.contrib.contenttypes.fields import GenericForeignKey, GenericRelation
   
   
   class PythonBasic(models.Model):
       course_name = models.CharField(max_length=32, verbose_name="課程名稱")
       # 定義反向查詢字段
       coupons = GenericRelation(to="Coupon")
   
       class Meta:
           db_table = "db_python_basic"
           verbose_name = "python課程資訊"
           verbose_name_plural = verbose_name
   
   
   class Oop(models.Model):
       course_name = models.CharField(max_length=32, verbose_name="課程名稱")
       coupon = GenericRelation(to="Coupon")
   
       class Meta:
           db_table = "db_oop"
           verbose_name = "面向對象課程資訊"
           verbose_name_plural = verbose_name
   
   
   class Coupon(models.Model):
       coupon_name = models.CharField(max_length=32, verbose_name="優惠卷名稱")
       # 關聯到ContentType的外鍵
       content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
       # 關聯表的資料所對應表的主鍵id
       object_id = models.PositiveIntegerField()
   
       # 這個字段在資料庫不存在, 這個字段幫助我們管理對應關系的
       content_object = GenericForeignKey("content_type", "object_id")
   
       class Meta:
           db_table = "db_coupon"
           verbose_name = "優惠卷資訊"
           verbose_name_plural = verbose_name
              

2. url.py

   from django.urls import re_path
   from .views import CourseView
   
   urlpatterns = [
       re_path(r"^course/$", CourseView.as_view())
   ]
              

3. views.py

   from django.shortcuts import HttpResponse
   from django.views import View
   from django.contrib.contenttypes.models import ContentType
   
   from .models import (
       PythonBasic,
       Oop,
       Coupon
   )
   from .app_serializers import BookSerializer
   
   
   class CourseView(View):
       def get(self, request):
           # 擷取表名
           # pb = ContentType.objects.get(app_label="serializer", model="pythonbasic")
           # 擷取表對象
           # pb_model = pb.model_class()
           # 擷取去表裡的第一條資料的對象
           # pb_obj = pb_model.objects.get(id=1)
           # print(pb_obj.course_name)
   
           # 擷取目前對象
           object_id = PythonBasic.objects.get(id=3)
           # 把目前對象插入到這個表中  要操作這個表隻能用content_object字段來操作  因為content_object是關系字段
           Coupon.objects.create(coupon_name="Python基礎通關優惠卷", content_object=object_id)
   
           return HttpResponse("ok")
              

4. 效果圖