Question

I have a count column in my tags table. I wanna increment tag count if a tag is just added to the post while updating, and it’s already inside db. I added this to my post model:

before_update :increment_tag

def increment_tag
  db_post = Post.find_by_id(self)
  self.tags.each do |tag|
    unless db_post.tags.include? tag
      tag.update_attribute("count", tag.count + 1)
    end
  end
end

I get the post from db and test if the current tag is already in db, if it is, nothing happens, if it’s not there, it should update count field. But for some reason this doesn’t work.

Answer 1

You should not have a Count column in a tag. You should in stead set up your models propperly so you could do the following:

db_post.tags.count

If you do it right, you can get this in your tag:

tag.post.tags.count

If your aim is to find how many times the tag is used in a post, in total, you can simply count the instances in the TagToPostColumn (if you got one), which you need to sine this is a many-to-many relation.

Then you do:

TagToPostColumn.where(tag_id: someTag.id).count

count is a standard attribute, and you should never have to keep track of this yourself, unless you actually need a column called count that tracks something other than the models you have in the database. But then it is a good idea to name it something else than count, since it can lead to ambiguous attributes.

Also, i find it very strange that you are doing this:

db_post = Post.find_by_id(self)

Why are you not just using the self parameter, in stead of doing a db lookup to find the post you already have.