Filter a contenttype with the content object's field

[Robin Lery]

I creating an app where users can post with its related tags:

class Tag(models.Model):
    name = models.CharField(max_length=255, unique=True)

class Post(models.Model):
    user = models.ForeignKey(User)
    body = models.TextField()
    tags = models.ManyToManyField(Tag)
    pub_date = models.DateTimeField(default=timezone.now)
    activity = GenericRelation(Activity)

class Activity(models.Model):
    actor = models.ForeignKey(User)
    verb = models.PositiveIntegerField(choices=VERB_TYPE)
    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
    object_id = models.PositiveIntegerField()
    content_object = GenericForeignKey('content_type', 'object_id')
    pub_date = models.DateTimeField(default=timezone.now)

What I want to do is filter the Activity with the a list of users, and a list of tags of the from list of Post objects.

Eg:

UserA created a new Post obect with tags(#class, #school)

UserB created a new Post object with tags(#professor, #teacher)

UserC created a new Post object with tags(#school, #university)

UserD created a new Post object with tags(#university, #school)

So say I want to filter Activity with user_list=[UserA, UserC] and tag_list = [#class, #teacher]

It should return:

UserA created a new Post obect with tags(#class, #school)

UserC created a new Post object with tags(#school, #university)
UserB created a new Post object with tags(#professor, #teacher)

To filter the Activity with users, I can query this way:
Activity.objects.filter(actor__in=user_list)

But, how do I filter Activity with the content_object's (i.e.Post) field (i.e. Post.tags)? Is this even possible? I cannot figure it out. And your help will be very much helpful. Thank you.

[Robin Lery]

I forgot to mention, there is another class:


class Photo(models.Model):
    user = models.ForeignKey(User)
    file = models.ImageField()

    tags = models.ManyToManyField(Tag)
    pub_date = models.DateTimeField(default=timezone.now)
    activity = GenericRelation(Activity)

So, filtering would be with the list of content_object's (i.e. Post of Photo) field (i.e. Post.tags or Photo.tags).

[Michel Rodrigues]

You may try add a related_query_name in the field activity:

activity = GenericRelation(Activity, related_query_name="post_tags")

https://docs.djangoproject.com/en/1.10/ref/contrib/contenttypes/#django.contrib.contenttypes.fields.GenericRelation.related_query_name

I make a test: 'michel' has a Post1 with tag1, tag2, tag3 and Post2 with tag1 and tag2. 'ana' has a Post3 just with tag3

>>> Activity.objects.filter(post_tags__tags__name='tag1')
<QuerySet [<Activity: michel>, <Activity: michel>]>

>>> Activity.objects.filter(post_tags__tags__name='tag2')
<QuerySet [<Activity: michel>, <Activity: michel>]>

>>> Activity.objects.filter(post_tags__tags__name='tag3')
<QuerySet [<Activity: michel>, <Activity: ana>]>


PS: sorry for my English, it's not my native language

[Michel Rodrigues]

Sorry, the point is a list of tags as argument, you can do this:

>>> Activity.objects.filter(tags_act__tags__name__in=['tag1','tag3']).distinct()
<QuerySet [<Activity: michel>, <Activity: michel>, <Activity: ana>]>


Without .distinct() django return duplicated objects:

>>> Activity.objects.filter(tags_act__tags__name__in=['tag1','tag3'])
<QuerySet [<Activity: michel>, <Activity: michel>, <Activity: michel>, <Activity: ana>]>

[Robin Lery]

Yes, this works. Thank you. But, as there are or will be more than one ContentType objects (i.e., Post model and Photo model), how do I iterate over it? Should I query them separately? Like

post_activities = Activity.objects.filter(post__tags__in=tags).distinct()

photos_activities = Activity.objects.filter(photo__tags__in=tags).distinct()

Or is there any better solution?

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