from django.db.models.signals import pre_delete
from django.dispatch.dispatcher import receiver
@receiver(pre_delete, sender=AddDateModel)
def mymodel_delete(sender, instance, **kwargs):
  # Pass false so FileField doesn't save the model.
  instance.file.delete(False)

# -*-coding:utf-8 -*-
from django.core.files.storage import FileSystemStorage
from django.http import HttpResponse
from django.conf import settings
import os, time, random
from app import utils
 
class FileStorage(FileSystemStorage):
  def __init__(self, location=settings.MEDIA_ROOT, base_url=settings.MEDIA_URL):
    #初始化
    super(FileStorage, self).__init__(location, base_url)
 
  #重写 _save方法
  def _save(self, name, content):
    #文件扩展名
    ext = os.path.splitext(name)[1]
    #文件目录
    d = os.path.dirname(name)
    # 定义文件名，源文件名，避开系统定义的随机字符串追加，所以避开不用name字段
    end = utils.find_last(str(content), ".")
    filename = ""
    if end != -1:
      filename = str(content)[:end]
    # 定义文件名，年月日时分秒随机数
    fn = time.strftime("%Y%m%d%H%M%S")
    fn = fn + "_%d" % random.randint(0,100)
    #重写合成文件名
    name = os.path.join(d, filename + fn + ext)
    #调用父类方法
    return super(FileStorage, self)._save(name, content)

# 获取字符串中指定字符最后一次出现的位置
def find_last(string,str):
  last_position=-1
  while True:
    position=string.find(str,last_position+1)
    if position==-1:
      return last_position
    last_position=position