Django补充

Posted 2021-02-12 bubu99

ContentType组件

ContentType是Django的内置的一个应用，可以追踪项目中所有的APP和model的对应关系，并记录在ContentType表中。
当项目做数据迁移后，会有很多django自带的表，其中就有django_content_type表

ContentType组件应用

• 在model中定义ForeignKey字段，并关联到ContentType表，通常这个字段命名为content-type
• 在model中定义PositiveIntergerField字段, 用来存储关联表中的主键，通常用object_id
• 在model中定义GenericForeignKey字段，传入上面两个字段的名字
• 方便反向查询可以定义GenericRelation字段

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

# Create your models here.


class Food(models.Model):
    """
    id      title
    1       面包
    2       牛奶
    """
    title = models.CharField(max_length=32)
    # 不会生成字段 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)


# 如果有40张表
# class Coupon(models.Model):
#     """
#     id      title          food_id    fruit_id
#     1       面包九五折         1         null
#     2       香蕉满10元减5元    null       2
#     """
#     title = models.CharField(max_length=32)
#     food = models.ForeignKey(to="Food")
#     fruit = models.ForeignKey(to="Fruit")


# class Coupon(models.Model):
#     """
#     id      title        table_id      object_id
#     1       面包九五折       1             1
#     2       香蕉满10元减5元  2             2
#     """
#     title = models.CharField(max_length=32)
#     table = models.ForeignKey(to="Table")
#     object_id = models.IntegerField()
#
#
# class Table(models.Model):
#     """
#     id      app_name       table_name
#     1       demo            food
#     2       demo            fruit
#     """
#     app_name = models.CharField(max_length=32)
#     table_name = models.CharField(max_length=32)


class Coupon(models.Model):
    title = models.CharField(max_length=32)
    # 第一步
    content_type = models.ForeignKey(to=ContentType, on_delete=None)
    # 第二步
    object_id = models.IntegerField()
    # 第三步 不会生成字段
    content_object = GenericForeignKey("content_type", "object_id")

models.py

from django.shortcuts import render
from rest_framework.views import APIView
from rest_framework.response import Response
from .models import Food, Coupon
from django.contrib.contenttypes.models import ContentType

# Create your views here.


class DemoView(APIView):

    def get(self, request):
        # 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)

        #查询面包都有哪些优惠券
        #定义了反向查询
        coupons = food_obj.coupons.all()
        print(coupons)

        # 如果没定义反向查询
        content = ContentType.objects.filter(app_label="app01", model="food").first()
        coupons = Coupon.objects.filter(content_type=content, object_id=1).all()
        print(coupons)

        # 优惠券查对象
        # 查询优惠券id=1绑定了哪个商品
        coupon_obj = Coupon.objects.filter(id=1).first()
        content_obj = coupon_obj.content_object
        print(coupon_obj.title,content_obj.title)

        # 通过ContentType表找表模型
        content = ContentType.objects.filter(app_label="app01", model="food").first()
        # 获得表model对象 相当于models.Applicance
        model_class = content.model_class()
        ret = model_class.objects.all()
        print(ret)

        return Response("ContentType测试")

views.py

media的配置

#静态文件
STATIC_URL = ‘/static/‘  
STATICFILES_DIRS=(
    os.path.join(BASE_DIR,‘static‘),  
)
# Media配置
MEDIA_URL = "media/"
MEDIA_ROOT = os.path.join(BASE_DIR, "media")

settings.py

from django.conf.urls import url, include
from django.contrib import admin
from django.views.static import serve
from new_luffy import settings


urlpatterns = [
    url(r‘^admin/‘, admin.site.urls),
    url(r‘^api/course/‘, include("course.urls")),

    # media路径配置
    url(r‘media/(?P<path>.*)$‘, serve, {‘document_root‘: settings.MEDIA_ROOT})
]

urls.py