from django.core.exceptions import ValidationError def check_speaker_event_camp_consistency(sender, instance, **kwargs): if kwargs['action'] == 'pre_add': from program.models import Speaker, Event if isinstance(instance, Event): # loop over speakers being added to this event for pk in kwargs['pk_set']: # check if this speaker belongs to a different Camp than the event does speaker = Speaker.objects.get(id=pk) if speaker.camp != instance.camp: raise ValidationError({'speakers': 'The speaker (%s) belongs to a different camp (%s) than the event does (%s)' % (speaker, speaker.camp, instance.camp)}) elif isinstance(instance, Speaker): # loop over events being added to this speaker for pk in kwargs['pk_set']: # check if this event belongs to a different Camp than the speaker does event = Event.objects.get(id=pk) if event.camp != instance.camp: raise ValidationError({'events': 'The event (%s) belongs to a different camp (%s) than the event does (%s)' % (event, event.camp, instance.camp)}) def check_speaker_camp_change(sender, instance, **kwargs): if instance.pk: for event in instance.events.all(): if event.camp != instance.camp: raise ValidationError({'camp': 'You cannot change the camp a speaker belongs to if the speaker is associated with one or more events.'})