User to Model relationship- implement a "like" feature on a Model

[amarshall]

Hi,

   I'm trying to implement likes on a Model in which 1 user will be able to like an a model (named "event") "once" and only once.

so, I have a model like this:

class Event(models.Model):

    user = models.ForeignKey(User)
    .         #other fields
    .
    likes = models.PositiveIntegerField(default=0,null=True)

How do I implement it so that only one user can "like" an event (increase by 1) ? Brainstorming I'm thinking should I make a new class called "like" and have it have "Event" as a foreign key and a oneToOne relationship with User ? not really sure how to go about doing this.

class Like(models.Model):
       
       event = models.ForeignKey(Event)
       
       user = model.ManyToMany(User)
       user_liked = models.BooleanField(default=false)
       total_count = models.PositiveIntegerField(default=0)

?   Then when an event is created a "Like" is created as well ? This may be doing to much and there's a simpler way?


      

[Mario Gudelj]

The other way would be to simply wire a cookie to user's browser and use js to disable the the like button if the cookie is present if you can get away with it. Not sure if you need to store that info against the user to see which items they liked...

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[amarshall]

Hmm, That may work. I should have also noted one thing. I'm actually using Django as the backend for mobile application. Both Android and iOS. So I'd like to do something like this, in the simplest matter:

pseudocode:
 
      get information from the server.
      if this_user HAS NOT "liked"  this event ,
              event_likes_count += 1
     else
          keep the like count the same. make like button inactive

[Tim Chase]

On 2014-08-25 17:00, amarshall wrote:
> Hmm, That may work. I should have also noted one thing. I'm
> actually using Django as the backend for mobile application. Both

> *Android* and iOS. So I'd like to do something like this, in the

> simplest matter:
>
> pseudocode:
>
> get information from the server.
> if this_user HAS NOT "liked" this event ,
> event_likes_count += 1
> else
> keep the like count the same. make like button inactive

You may want to try phrasing the problem as "select count of all the
likes where the event=$THIS_EVENT and the user != $THIS_USER" which
is pretty close to the underlying SQL and shouldn't be too hard to
translate into a a Django query. Something like this untested

# [models.py]
class Event(Model):
likes = ManyToMany(through="Like")
# ...

class Like(Model):
event = ForeignKey(Event)
user = ForeignKey(User)
class Meta:
unique_together = [
("event", "user"),
]

# [views.py]
this_event = #...
this_user = #...
Like.objects.filter(event=this_event).exclude(user=this_user).Count(id)

As mentioned, it's untested, but should get you pretty close.


-tkc

[amarshall]

Thanks ! I'll get to work on that and see how it goes!

[shmengie]

models.py:

class Like(models.Model):
    event = models.ForeignKey(Event)
    user = model.ForeignKey(User)


    class Meta:
        unique_together = ("event", "user")

Now you can count Likes for a given event

likes = Like.objects.filter(event='BizBangBoom').annotate(number_of_entries=Count('entry'))

The unique_together Meta enforces limit of one like per user, per event.

If a user un-likes an event, delete the envent - user record