Django reverse lookup of foreign keys

Question

I have a venue, this venue has many events happening there. My models look like this:

class Venue(models.Model):
    title = models.CharField(max_length=200)
    date_published = models.DateTimeField('published date',default=datetime.now, blank=True)
    venue_latitude = models.CharField(max_length=200)
    venue_longitude = models.CharField(max_length=200)
    venue_address = models.CharField(max_length=200)
    venue_city = models.CharField(max_length=200)
    venue_state = models.CharField(max_length=200)
    venue_country = models.CharField(max_length=200)
    description = models.TextField()
    def __unicode__(self):
        return u'%s' % (self.title)

class Event(models.Model):
    title = models.CharField(max_length=200)
    date_published = models.DateTimeField('published date',default=datetime.now, blank=True)
    date_start = models.DateTimeField('start date')
    date_end = models.DateTimeField('end date')
    def __unicode__(self):
        return self.title
    description = models.TextField()
    price = models.IntegerField(null=True, blank=True)
    venue = models.ForeignKey(Venue)

I'd like to display all the events that are happening at a certain venue. How can I do that? My current view looks like:

def detail(request, venue_id):
    venue = get_object_or_404(Venue, pk=venue_id)
    return render(request, 'venue-detail.html', {'venue': venue})

What module do these fields relate too description = models.TextField()? — donkeyboy72, Mar 09 '13 at 03:51
Actually, these two models are each in their own app, I just posted them together to explain the point :) — FLX, Mar 09 '13 at 05:00

score 172 · Accepted Answer · edited Apr 08 '20 at 01:02

172

You can use events = venue.event_set to go the other way.

Note that venue.event_set is a manager object, like Event.objects, so you can call .all, .filter, .exclude and similar on it to get a queryset.

See the Django documentation

edited Apr 08 '20 at 01:02

Fifi

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answered Mar 09 '13 at 04:41

Ric

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Great! THanks for that. However, If I want to iterate over the events (for i in events) I'm getting "'RelatedManager' object is not iterable" – FLX Mar 09 '13 at 04:53
How did you change it to QueryObject ? – mp3por Feb 06 '16 at 13:27
7

@mp3por venue.event_set.all() or venue.event_set.filter(), usually. – aptwebapps Mar 05 '16 at 09:26
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If anyone stills sees the error `AttributeError: 'Foo' object has no attribute 'bar_set'`, you might want to check if `related_name` is set on the `ForeignKey`/`OneToOneField`/`ManyToManyField` of the child model (`Bar`) referencing the parent model (`Foo`). – Bartleby May 24 '20 at 12:54
Will this lookup be fast ? should he add foregin key to Venue ? will it make it faster ? – Sion C May 06 '21 at 09:10
Note that if a "related_name" has been set on the foreign key def, you do not need to append "_set". – RunLoop Jul 28 '22 at 03:56
Be aware that setting `related_name="+"` on the `ForeignKey` will cause this to not be possible ([source](https://docs.djangoproject.com/en/4.2/ref/models/fields/#django.db.models.ForeignKey.related_name)). – Akaisteph7 Jun 14 '23 at 16:27

score 10 · Answer 2 · edited May 23 '17 at 11:33

10

To those who have "'RelatedManager' object is not iterable"

Add all to retrieve the elements from the manager.

{% for area in world_areas.all %}

https://stackoverflow.com/a/16909142/2491526 (cannot add this in comment to the first answer)

edited May 23 '17 at 11:33

Community

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answered May 20 '15 at 11:44

Apex

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You just saved my day [link](https://stackoverflow.com/q/65057186/13823230). – shaan Nov 29 '20 at 12:08
1

I was about to create mess in my models before I found this :D – PowerAktar Dec 30 '20 at 19:16

score 6 · Answer 3 · edited Mar 08 '14 at 04:10

6

Go the other way round. Use Event model.

def detail(request, venue_id):
    venue = Event.objects.filter(venue__id=venue_id)
    return render(request, 'venue-detail.html', {'venue': venue})

PS: I have never used get_object_or_404(). Modify code accordingly.

edited Mar 08 '14 at 04:10

alecxe

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answered Mar 09 '13 at 03:51

rjv

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So what can I use in my template to display the venue title and all the events happening at this venue? – FLX Mar 09 '13 at 03:53
1

in the template use {{ event.venue.title }} or as per your variables {{ venue.venue.title }} :) `{% for i in venue %} {{ i.venue.title }}` – rjv Mar 09 '13 at 03:55
I get that, but how do I display all the events happening at this venue? – FLX Mar 09 '13 at 04:16
the filter returns an array containing all the events that happen at the venue.loop over the array in the templates using the `for` – rjv Mar 09 '13 at 04:54
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`venue = Event.objects.filter(venue__id=venue_id)` I think this expression will return QuerySet of Event object instead of Venue object. – smilingwang Sep 11 '18 at 03:23
@smilingwang read the question being asked. – boatcoder Feb 27 '22 at 00:30

score 0 · Answer 4 · answered Jul 21 '23 at 18:23

You can use venue.event_set.all() to get all the events that are happening at a certain venue as shown below:

def detail(request, venue_id):
    venue = get_object_or_404(Venue, pk=venue_id)
    events = venue.event_set.all() # Here
    return render(request, 'venue-detail.html', {'events': events})

Django reverse lookup of foreign keys

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