第十六章 Django框架——ContentType组件

第十六章 Django框架——ContentType组件

一、ContentType应用场景

二、ContentType组件使用

一、ContentType应用场景

需求：现在学校有专题课、试听课、学位课三类课程，三种课程有不同的价格策略，请设计表结构。

设计方案一：

一个课程表，包含学位课和专题课，一个价格策略表，一对多关联

设计方案二：

学位课表，专题课表，试听课表，价格策略表（在价格策略课表中加入多个FK跟课程表做关联）：后期再加其它课程，可维护性差

 

二、ContentType组件使用

设计方案三：

通过Django提供的ContentType表，来构建关联

contenttype表位置：

contenttype表无需创建，生成数据库时自动创建

这些是我们刚才创建的表

导入模块：

# models.py内使用
from django.contrib.contenttypes.models import ContentType

from django.contrib.contenttypes.fields import GenericForeignKey, GenericRelation

实现如下需求：

1.为专题课，添加三个价格策略

urls.py

urlpatterns = [
    url(r'^admin/', admin.site.urls),
    url(r'^test/',views.addPrice)
]

views.py

from django.shortcuts import *
from app01.models import *
# Create your views here.

def addPrice(request):
    # 为django专题课，添加三个价格策略
    course = Course.objects.filter(pk=1).first()
    # content = ContentType.objects.filter(model='course').first()
    # PricePolicy.objects.create(period=1,price=0,object_id=course.pk,content_type_id=content.pk)
    # PricePolicy.objects.create(period=3,price=49,object_id=course.pk,content_type_id=content.pk)
    # PricePolicy.objects.create(period=6,price=99,object_id=course.pk,content_type_id=content.pk)
    # 这一句话与上面四行意思相同，节约代码
    PricePolicy.objects.create(period=12,price=300,content_obj=course)
　　

　　 # 为python全栈开发学位课，加一个价格策略
　　 degree = DegreeCourse.objects.first(pk=1).first()
　　 PricePolicy.objects.create(period=5,price=18000,content_type=degree)

return HttpResponse('ok')

models.py

from django.db import models

# Create your models here.
from django.contrib.contenttypes.models import ContentType
from django.contrib.contenttypes.fields import GenericForeignKey, GenericRelation

class Course(models.Model):
    title = models.CharField(max_length=32)

class DegreeCourse(models.Model):
    title = models.CharField(max_length=32)

class PricePolicy(models.Model):
    period = models.IntegerField()
    price = models.PositiveIntegerField()
    content_type = models.ForeignKey(to=ContentType,null=True)
    # GenericForeignKey不会在数据库生成字段，只用于查询和插入
    object_id = GenericForeignKey('content_type','object_id')

2.查询所有价格策略，并且显示对应的课程名称

urls.py

urlpatterns = [
    url(r'^admin/', admin.site.urls),
    url(r'^test/',views.addPrice)
]

views.py

from django.shortcuts import *
from app01.models import *
# Create your views here.

def addPrice(request):
    # 查询所有价格策略，并且显示对应的课程名称
    ret = PricePolicy.objects.all()
    for price in ret :
        print(price.content_obj.title)
    return HttpResponse('ok')

models.py

from django.db import models

# Create your models here.
from django.contrib.contenttypes.models import ContentType
from django.contrib.contenttypes.fields import GenericForeignKey, GenericRelation

class Course(models.Model):
    title = models.CharField(max_length=32)

class DegreeCourse(models.Model):
    title = models.CharField(max_length=32)

class PricePolicy(models.Model):
    period = models.IntegerField()
    price = models.PositiveIntegerField()
    content_type = models.ForeignKey(to=ContentType,null=True)
    # GenericForeignKey不会在数据库生成字段，只用于查询和插入
    object_id = GenericForeignKey('content_type','object_id')

3.通过课程id，获取课程信息和价格策略

urls.py

urlpatterns = [
    url(r'^admin/', admin.site.urls),
    url(r'^test/',views.addPrice)
]

views.py

from django.shortcuts import *
from app01.models import *
# Create your views here.

def addPrice(request):

    # 通过课程id，获取课程信息和价格策略
    course = Course.objects.filter(pk=1).first()
    print(course.policy.all())
    for i in course.policy.all():
        print(i.price)
    # 查专题
    degree = DegreeCourse.objects.filter(pk=1).first()
    for i in degree.policy.all():
        print(i.price)
    return HttpResponse('ok')

models.py

from django.db import models

# Create your models here.
from django.contrib.contenttypes.models import ContentType
from django.contrib.contenttypes.fields import GenericForeignKey, GenericRelation

class Course(models.Model):
    title = models.CharField(max_length=32)
    # 不会再数据库生成字段，只用来查询
    policy = GenericRelation('PricePolicy',object_id_field='object_id',content_type_field='contentType')

class DegreeCourse(models.Model):
    title = models.CharField(max_length=32)

class PricePolicy(models.Model):
    period = models.IntegerField()
    price = models.PositiveIntegerField()
    content_type = models.ForeignKey(to=ContentType,null=True)
    # GenericForeignKey不会在数据库生成字段，只用于查询和插入
    object_id = GenericForeignKey('content_type','object_id')