Override save method to add list in the many to many field

[Robin Lery]

I have this model to save post from the users:

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

def add_tags(obj_id, body):
    object = Post.objects.get(id=obj_id)
    tag_list = [Tag.objects.create(name=word) for word in body.split()]
    for tag in tag_list:
        object.tags.add(tag)

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

    def save(self, *args, **kwargs):
        super(Post, self).save(*args, **kwargs)
        if self.body:
            body = self.body
            obj_id = self.id
            add_tags(obj_id, body)

So whenever a user post something, I would like to check if there's any hash-tag used inside the body. If there are tags, then fetch the tags inside the list.

But when I am posting, the tag objects are created, but they are not adding for the Post.tags fields.

post.body example = Check #from the http://somesitedotcom/page#idtop #hell yeah!

What am I doing wrong here?