[Django]-Django: accessing ManyToManyField objects after the save

This is how I worked around this, indeed baffling, behavior. Connect a signal receiver to models.signals.m2m_changed event, this get’s triggered each time a m2m field is changed. The inline comments explain why.

class Gig(models.Model):
    def slugify(self):
        # Add venue name, date and artists to slug
        self.slug = slugify(self.venue.name) + "-"
        self.slug += self.date.strftime("%d-%m-%Y") + "-"
        self.slug += "-".join([slugify(artist.name) for artist in self.artists.all()]) 
        self.save()


@receiver(models.signals.m2m_changed, sender=Gig.artist.through)
def gig_artists_changed(sender, instance, **kwargs):
    # This callback function get's called twice. 
    # 1 first change appears to be adding an empty list
    # 2nd change is adding the actual artists
    if instance.artist.all() and not instance.slug:                                                                                                                                                               
        instance.slugify()