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# Signals

New in version 0.5.

Note

Signal support is provided by the excellent blinker library and will gracefully fall back if it is not available.

The following document signals exist in MongoEngine and are pretty self-explanatory:

> - mongoengine.signals.pre_init
> - mongoengine.signals.post_init
> - mongoengine.signals.pre_save
> - mongoengine.signals.post_save
> - mongoengine.signals.pre_delete
> - mongoengine.signals.post_delete
> - mongoengine.signals.pre_bulk_insert
> - mongoengine.signals.post_bulk_insert

Example usage:

    from mongoengine import *
    from mongoengine import signals

    class Author(Document):
        name = StringField()

        def __unicode__(self):
            return self.name

        @classmethod
        def pre_save(cls, sender, document, **kwargs):
            logging.debug("Pre Save: %s" % document.name)

        @classmethod
        def post_save(cls, sender, document, **kwargs):
            logging.debug("Post Save: %s" % document.name)
            if 'created' in kwargs:
                if kwargs['created']:
                    logging.debug("Created")
                else:
                    logging.debug("Updated")

    signals.pre_save.connect(Author.pre_save, sender=Author)
    signals.post_save.connect(Author.post_save, sender=Author)

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