Django模型:delete()未触发

Question

我有一个模特:

class MyModel(models.Model):
 ...
    def save(self):
        print "saving"
        ...
    def delete(self):
        print "deleting"
        ...

save() - 方法被触发,但delete()不是.我使用最新的svn-Version(Django 1.2版pre-alpha SVN-11593),关于http://www.djangoproject.com/documentation/models/save_delete_hooks/上的文档,这应该可行.有任何想法吗？

Answer 1

我认为您可能正在使用管理员的批量删除功能,并且正在遇到管理员的批量删除方法未调用的事实delete()(请参阅相关的故障单).

我在过去通过编写用于删除模型的自定义管理操作来解决这个问题.

如果您没有使用管理员的批量删除方法(例如,您单击对象编辑页面上的删除按钮),则会发生其他事情.

请在此处查看警告:

QuerySet.delete()出于效率原因,"删除所选对象"操作会使用,这有一个重要的警告:delete()不会调用模型的方法.

如果您希望覆盖此行为,只需编写一个自定义操作,以您首选的方式完成删除 - 例如,通过调用Model.delete()每个选定的项目.

有关批量删除的更多背景信息,请参阅有关对象删除的文档.

我的自定义管理模型如下所示:

from photoblog.models import PhotoBlogEntry
from django.contrib import admin    

class PhotoBlogEntryAdmin(admin.ModelAdmin):
    actions=['really_delete_selected']

    def get_actions(self, request):
        actions = super(PhotoBlogEntryAdmin, self).get_actions(request)
        del actions['delete_selected']
        return actions

    def really_delete_selected(self, request, queryset):
        for obj in queryset:
            obj.delete()

        if queryset.count() == 1:
            message_bit = "1 photoblog entry was"
        else:
            message_bit = "%s photoblog entries were" % queryset.count()
        self.message_user(request, "%s successfully deleted." % message_bit)
    really_delete_selected.short_description = "Delete selected entries"

admin.site.register(PhotoBlogEntry, PhotoBlogEntryAdmin)

Answer 2

我知道这个问题很古老,但我刚刚再遇到这个问题,并希望补充一点,您可以随时将代码移动到pre_delete或post_delete信号,如下所示:

from django.db.models.signals import pre_delete
from django.dispatch.dispatcher import receiver

@receiver(pre_delete, sender=MyModel)
def _mymodel_delete(sender, instance, **kwargs):
    print("deleting")

它适用于管理员的批量删除操作(至少从1.3.1开始).

Answer 3

管理员调用的批量操作queryset.delete().

您可以覆盖查询集的.delete()方法,因此它始终执行1对1的对象删除.例如:

在managers.py中:

from django.db import models
from django.db.models.query import QuerySet

class PhotoQueryMixin(object):
    """ Methods that appear both in the manager and queryset. """
    def delete(self):
        # Use individual queries to the attachment is removed.
        for photo in self.all():
            photo.delete()

class PhotoQuerySet(PhotoQueryMixin, QuerySet):
    pass

class PhotoManager(PhotoQueryMixin, models.Manager):
    def get_query_set(self):
        return PhotoQuerySet(self.model, using=self._db)

在models.py中:

from django.db import models

class Photo(models.Model):
    image = models.ImageField(upload_to='images')

    objects = PhotoManager()

    def delete(self, *args, **kwargs):
        # Note this is a simple example. it only handles delete(),
        # and not replacing images in .save()
        super(Photo, self).delete(*args, **kwargs)
        self.image.delete()

Answer 4

使用django v2.2.2，我用下面的代码解决了这个问题

模型.py

class MyModel(models.Model):
    file = models.FileField(upload_to=<path>)

    def save(self, *args, **kwargs):
        if self.pk is not None:
            old_file = MyModel.objects.get(pk=self.pk).file
            if old_file.path != self.file.path:
                self.file.storage.delete(old_file.path)

        return super(MyModel, self).save(*args, **kwargs)

    def delete(self, *args, **kwargs):
        ret = super(MyModel, self).delete(*args, **kwargs)
        self.file.storage.delete(self.file.path)
        return ret

管理文件

class MyModelAdmin(admin.ModelAdmin):

    def delete_queryset(self, request, queryset):
        for obj in queryset:
            obj.delete()

对于 DefaultAdminSite，如果用户具有正确的权限，则调用 delete_queryset，唯一的区别是原始函数调用queryset.delete()不会触发模型delete方法。这效率较低，因为不再是批量操作，但它保持文件系统干净 =)