Python django.db.models.signals 模块，pre_save() 实例源码

def user_pre_save(sender, instance=None, raw=False, **kwargs):
    user = instance
    attrs = ExpirySettings.get()
    # We're saving the password change date only for existing users
    # Users just created should be taken care of by auto_now_add.
    # This way we can assume that a User profile object already exists
    # for the user. This is essential, because password change detection
    # can happen only in pre_save, in post_save it is too late.
    is_new_user = user.pk is None
    if is_new_user or raw:
        return
    if attrs.date_changed:
        update_date_changed(user, attrs.date_changed)

    # User has been re-activated. Ensure the last_login is set to None so
    # that the user isn't inactivated on next login by the AccountExpiryBackend
    current_user = sender.objects.get(pk=user.pk)
    if not current_user.is_active and user.is_active:
        user.last_login = None

def __init__(self, create=True, update=True, delete=True, custom=None):
        from actionslog.receivers import action_log_create, action_log_update, action_log_delete

        self._registry = {}
        self._signals = {}

        if create:
            self._signals[post_save] = action_log_create
        if update:
            self._signals[pre_save] = action_log_update
        if delete:
            self._signals[post_delete] = action_log_delete

        if custom is not None:
            self._signals.update(custom)

def pre_save(self, instance, *args, **kwargs):
    from django.utils.text import slugify
    if not instance.slug:
        instance.slug = slugify(self.slug_source)

def update_domain_serial_when_interface_deleted(sender, instance, **kwargs):
    if instance.domain is not None:
        domain = instance.domain
        domain.domain_serial += 1
        domain.save()

    if instance.ip4address is not None:
        subnet = instance.ip4address.subnet
        subnet.domain_serial += 1
        subnet.save()

# @receiver(pre_save, sender=Domain)
# def update_domain_serial_when_domain_is_saved(sender, instance, **kwargs):
#    instance.domain_serial = format_domain_serial_and_add_one(instance.domain_serial)

def update_zipfile(sender, instance, **kwargs):
    """ Delete zip file on pre_save. This is needed in case of updation of 
        zip file, where the older file should be deleted from the location"""
    if instance.pk:
        details = SponsorProjectDetailsSubFields.objects.get(pk=instance.pk)
        if details.zip_file and details.zip_file.url != instance.zip_file.url:
            storage, path = details.zip_file.storage, details.zip_file.path
            storage.delete(path)