ContentType组件

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如图, 每一个课程类型对应一张表, 每一门课程都有不同的价格周期对应的价格, 所以价格表会有一个表名字段对应到ContentType表的pk, 但是这样每给一门课程加上价格策略都要有如下步骤

1. 拿到课程id

2. 拿到表名, 通过表名拿到ContentType表对应的id

3. 往价格表里面添加数据

通过课程拿到价格

1. 拿到表名

2. 通过ContentType表拿到对应的表名id

3. 在价格表通过表名id与课程id拿到价格

很麻烦!!!!

Django给我们提供了ContentType组件, 自带ContentType这个表

用法:

模型层:

from django.db import models
from django.contrib.contenttypes.models import ContentType
from django.contrib.contenttypes.fields import GenericForeignKey, GenericRelation

# Create your models here.
# 学位课
class Course1(models.Model):
    id = models.AutoField(primary_key=True)
    name = models.CharField(max_length=32)
    # 通过课程拿到价格时用的, 参数一:价格表,参数与参数三都为价格表的字段
    policy = GenericRelation('PricePolicy', object_id_field='object_id', content_type_field='contentType')


# 专题课
class Course2(models.Model):
    id = models.AutoField(primary_key=True)
    name = models.CharField(max_length=32)
    policy = GenericRelation('PricePolicy', object_id_field='object_id', content_type_field='contentType')

# 轻客    
class Course3(models.Model):
    id = models.AutoField(primary_key=True)
    name = models.CharField(max_length=32)
    policy = GenericRelation('PricePolicy', object_id_field='object_id', content_type_field='contentType')

# 价格表
class PricePolicy(models.Model):
    # 跟ContentType表做外键关联
    contentType = models.ForeignKey(to=ContentType)
    # 正整数,课程id
    object_id = models.PositiveIntegerField()
    content_obj = GenericForeignKey('contentType', 'object_id')
    
    
    period = models.CharField(max_length=32)
    price = models.FloatField()

视图层:

1. 存价格
def test(request):
    course = models.Course1.objects.filter(pk=1).first()
    # 只需传入课程对象,周期,价格,就会自动存入表id与课程id
    models.PricePolicy.objects.create(
        period='60', price=800, content_obj=course
    )
    return HttpResponse('ok')

2. 询所有价格策略，并且显示对应的课程名称
def test(request):
    ret=models.PricePolicy.objects.all()
    for i in ret:
        print(i.price)
        print(i.period)
        # content_obj 就是代指关联的课程，或者学位课程的那个对象
        print(type(i.content_obj))
        print(i.content_obj.name)
    return HttpResponse('ok')

3. 通过课程id，获取课程信息和价格策略
def test(request):
    course=models.Course1 .objects.filter(pk=1).first()
    print(course.policy.all())
    return HttpResponse('ok')