Django课程内容数据模型

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)

Django课程内容数据模型

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