I have a model
class EventArticle(models.Model):
event = models.ForeignKey(Event, related_name='article_event_commentary')
author = models.ForeignKey(Person)
and another model
class Event(models.Model):
attendies = models.ManyToManyField(Person, related_name="people")
How do I restrict an author
to only objects that are also attendies
?
Typically, the ForeignKey
limit_choices_to
argument is your friend in situations like this. (See https://docs.djangoproject.com/en/1.8/ref/models/fields/#django.db.models.ForeignKey.limit_choices_to )
You could restrict the author to a list of users of have attended any event. However, even doing that is far from ideal:
# don't try this at home, this will be excruciatingly slow...
def author_options():
all_attendee_ids = []
for e in Event.objects.all():
for a in e.attendies.all():
all_attendee_ids.append(a.id)
return {'author': Person.objects.filter(id_in=set(all_attendee_ids)).id}
# requires Django 1.7+
class EventArticle(models.Model):
event = models.ForeignKey(Event, related_name='article_event_commentary')
author = models.ForeignKey(Person, limit_choices_to=author_options)
However, even though you didn't explicitly state it in your question, I suspect you want authors to be limited to a set of attendees from that particular event, ie the same event as specified in the EventArticle model's event field.
In which case, this brings about two problems which I don't believe can be solved cleanly:
As using limit_choices_to isn't going to work here, there probably isn't a way to fix this cleanly. You could add a method to your EventArticle model which will give you a list of potential authors like so...
class EventArticle(models.Model):
event = models.ForeignKey(Event, related_name='article_event_commentary')
author = models.ForeignKey(Person)
def author_options(self):
if self.event:
return self.event.attendies.all()
else:
return []
...but you will still need to do some legwork to make those options available to the UI so the user can select them. Without knowing more about your setup, I'd be guessing if I tried to answer that part.
您可以重写EventArticle模型的save()来确保它。
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.