Meta类实现

class News(models.Model):    title = models.CharField(max_length=35)    desc = models.CharField(max_length=100)    thumbnail = models.URLField()    content = models.TextField()    pubtime = models.DateTimeField(auto_now_add=True)    category = models.ForeignKey(NewsCategory, on_delete=models.SET_NULL, null=True)    author = models.ForeignKey(User, on_delete=models.SET_NULL, null=True)    class Meta:        ordering = ['-pubtime']  # 以后进行News.object提取数据时，按照指定字段的排序提取数据