版权声明:本文为博主原创文章,未经博主允许不得转载。 https://blog.csdn.net/chengqiuming/article/details/85912657
一 编辑mysite/course/models.py
from django.db import models
from django.contrib.auth.models import User
from slugify import slugify
from .fields import OrderField
class Course(models.Model):
user = models.ForeignKey(User, related_name='courses_user')
title = models.CharField(max_length=200)
slug = models.SlugField(max_length=200, unique=True)
overview = models.TextField()
created = models.DateTimeField(auto_now_add=True)
student = models.ManyToManyField(User, related_name="courses_joined", blank=True)
class Meta:
ordering = ('-created',)
def save(self, *args, **kargs):
self.slug = slugify(self.title)
super(Course, self).save(*args, **kargs)
def __str__(self):
return self.title
# 实现视频和文件分用户存放
def user_directory_path(instance, filename):
return "courses/user_{0}/{1}".format(instance.user.id, filename)
class Lesson(models.Model):
user = models.ForeignKey(User, related_name='lesson_user')
course = models.ForeignKey(Course, related_name='lesson')
title = models.CharField(max_length=200)
# 接收上传的视频
video = models.FileField(upload_to=user_directory_path)
description = models.TextField(blank=True)
# 接收上传附件
attach = models.FileField(blank=True, upload_to=user_directory_path)
created = models.DateTimeField(auto_now_add=True)
# 用来存储某课程内容在响应的课程标题Course中的序号
order = OrderField(blank=True, for_fields=['course'])
class Meta:
# 按照order进行排序
ordering = ['order']
def __str__(self):
return '{}.{}'.format(self.order, self.title)
二 创建子定义字段属性
from django.db import models
from django.core.exceptions import ObjectDoesNotExist
# 要哦对象排序的序号,其值为整数,所以继承PositiveIntegerField
class OrderField(models.PositiveIntegerField):
def __init__(self, for_fields=None, *args, **kwargs):
self.for_fields = for_fields
super(OrderField, self).__init__(*args, **kwargs)
# Django字段属性中,都继承了Field类,pre_save就是Field类中的一个方法
# 该方法的作用是在数据保存之前进行预处理,在某个具体字段属性中
# 因为特殊的需求,常常将Field类中的这个方法重写
# 该方法具体实现:将最终实例的序号记录下来
def pre_save(self, model_instance, add):
# 判断当前实例是否有某个属性
# 计算新增一条数据后的序号
if getattr(model_instance, self.attname) is None:
try:
# 得到当前实例的所有记录
qs = self.model.objects.all()
print(qs)
# <QuerySet [<Lesson: 0.大一英文>, <Lesson: 0.春节>, <Lesson: 1.传统佳节>]>
if self.for_fields:
query = {field: getattr(model_instance, field) for field in self.for_fields}
qs = qs.filter(**query)
last_item = qs.latest(self.attname)
# 得到最后一条记录,并加1
value = last_item.order + 1
except ObjectDoesNotExist:
value = 0
setattr(model_instance, self.attname, value)
# 得到新增记录的序号
return value
else:
# 调用父类的pre_save,但不会在数据库中增加记录
return super(OrderField, self).pre_save(model_instance, add)